The goal of this ible is to detail how I went about making tomato sauce out of 600 lbs of tomatoes. Fair warning, it was still a long day of work... but it was just that, all done in a single day.

For context, this was done with two friends, and we each had some duplicate equipment which sped things up, I will detail estimated times for having only one burner etc.

Step 1: Material

The mandatory items are

very large pot (30 L / QT or more)
A decent size pot (5L / 1 gallon)
Food grade buckets (5 gallon / 20 L)
Knife to remove bad parts of the tomatoes
A burner
- If you want to save money, a burner + pot combo will work nicely, but the burners sold alone can usually output more energy, which saves time in the boiling process.
- If you are going large scale, like I am doing here, you should seriously consider one of these triple units.
A tomato strainer / juicer. They vary in price and quality. The cheaper ones will need more frequent cleanings to keep going, so go with what works for you. The one linked worked best when cleaned every two bushels (100 lbs of tomatoes), but could easily go 4 bushels. A cheaper one we also had, had to be cleaned non stop, and unblanched tomatoes were too much for it.
a very long spatula, or a stick (I used both)
Mason jars: minimum 33 oz or 1 L per 5 lbs of tomatoes, up to 1.5x that if you use the recipe that produces more volume that I discuss later.
a wide mouth funnel for canning

Step 2: Ingredients

Food; this varies a lot by your recipe. In this case, I am just making a base tomato sauce that will be used in many applications (stews, chili, spaghetti sauce, etc.) so keep it basic.

For the tomatoes, you will have to figure out where to get it, in my case I can get half bushels (25 lbs) for 6$ at the grocery store. Talking to a farmer can be worth it.
Herbes de Provence (a mix of Basil, Marjoram, Thyme, Parsley, Tarragon, Rosemary, Fennel Seeds, Mint, and Oregano). I went to my local bulk barn and bought everything they had... like the full display container.
garlic (I use at least 2 full bunches per bushel)
onions ( 5 lbs per bushel)
lots of ground pepper
salt
a bit of sugar (you will need about 1/2 cup per 100 lbs of tomatoes)
whatever else...

Step 3: Prepare the Onions and Garlic

Before hand (possibly the night before), chop up the onions and garlic and fry them up. I used a food processor I borrowed to chop it all up faster, but if you go with bigger chunks, that food processor did not make things THAT much faster all things considered.

Fry them up before putting them in the sauce. For the onions, they were drained of their water (used in a soup!) and I added about 1L of oil to the 20 lbs of onions and cooked it up. The garlic was just plopped in a bot of simmering oil to fry them; makes the oil and the garlic quite delicious. That oil can then be added to the sauce.

Step 4: Clean the Tomatoes

Clean 'em up, remove the nasty bits, then run them through the strainer to remove the peel and seeds. This reduces the acidity and makes the preserving process more effective.

Step 5: Mix It All Up and Simmer It

Having a single burner means that you just do a large pot, and top it up with fresh sauce as it boils down, this does take a bit longer. More burners = less time. If you are going from scratch and need multiple burners, get one of these triple units (I'm doing that for next year). They have have a solid amount of power per burner, and are a great value proposition.

Once you mix it up, boil it until it thickens up. An important point in how much sauce you will get is how much herbs you put in. Dried herbs absorb water and make a huge difference. My friends who use herbs very sparingly (and have a much more traditional marinara sauce for it) get about 18 L / QT per 100 lbs of tomatoes. I got about 27.... That is quite a bit more, and it's all thanks to those extra dried herbs, because they soak up a lot of water. You can use tomato paste to get a similar thickening result, but then you need more jars, so might as well keep that paste on the shelves.

My rule of thumbs for herbs is at least 5-6 cups of herbs per bushel (100 lbs). If it looks like you have enough, double it! If you are worried because it's all you can smell, that's probably the right amount :)

Make sure you add sugar to cut the acidity. It really doesn't take much, about 1-2 table spoons per 10L of sauce will make a huge difference in the acidity. Other than than, season as you like, a bit of salt and a generous serving of pepper is always good. If your onions were not cooked with oil, you will probably want to add some. At this point, you can use my friend's idea and fry your garlic in the oil to help get the taste evenly spread.

ps. That "mountain" of sugar in there is floating on herbs (so it looks bigger than it is), and is for about 60 L of raw sauce (1 bushel's worth). There is only about a handful of sugar.

Step 6: Can It You!

I won't get into the details of how to prepare your jars too much, this is about the recipe and the method to manage the bulk produce. However, please make sure you do the following

leave some air in the jar (prevents botulism)
wipe the lip of the jar before putting the lid (prevents a pathway for pathogens)
if you aren't going to sterilize everything because "the sauce is hot enough" at least make sure you clean it all before you use it
- If you are willing to go half way on the sterilization, boil the lids, that is the most important part. The jars do get filled with boiling liquid, and I will concede that they will most likely be cleaned by this in the case of sauce in a rolling boil. The lids are the main point of failure, and are super easy to boil for 10 minutes.

When it comes time to can, just use a large ladle, or a small pot to pick up the sauce and put it in the jars. Using a wide mouth funnel will make this a breeze. Not using one will make this a mess and a pain. Make sure you do this while the sauce is still boiling, and clean the rim for drips, to make sure the jar gets that vacuum seal.

Check your lids to see if they have popped after 12 hours. If they did not, you can fix them. The main failures are

reusing old lids where the seal was no longer good, chuck it (the lid, keep the pot and sauce!).
improperly wiped lip, which allowed air in
lid was not properly seated: that metal ring is only there to make sure that the lid is properly centred and seated, and does not get knocked off. Once the tops pop, and your preserve is stored in a place where you won't move it, you could re-use the rings if you were in a situation where you do a lot of preserves and have lots of jars with no lids (buying just the lids is dirt cheap, buying lids + rings is annoyingly expensive).

To fix them, you can eat the contents, or just change the lid and re-boil that small amount of sauce before you put it back in.