I call this V-12 (It's in the hot peppers)
I use a food mill with a single screw and 1mm holes on the extraction screen.
Per 12 qt of juice extracted from tomatoes:
Using a centrifugal juicer make the following mix; (This should produce about 12 oz)
1 cup onion
1 cup parsley
1 cup celery
1 large carrot
1 cup sweet pepper
12 clove garlic
1 medium jalapeno or garden salsa pepper (optional) (NO SEEDS)

Mix the extract with tomato juice and add the following to a 16qt stock pot:
2 Tbs black pepper
2 Tbs horseradish
6 Tbs canning or sea salt
1-1/2 cup sugar

Bring to a boil, then reduce to a slow rolling simmer for 1-1/2 hours. Scrape the foam on a regular basis from the top of the mix.

I no longer water bath my jars. I put them in the oven at 190 deg. Pasteurization is 180 deg for 1 sec. The lids are in a water bath by the stock pot same basic temp.

I pull jars one at a time and stage next to the stock pot. Decanting with a 6 oz ladle and funnel to the bottom of the funnel. Magnetic pick up the lid then place and snug the ring down.

Juice and sauce tomatoes differ in water content substantively. If using sauce tomatoes (roma or similar) you can reduce juice and add water. Play with taste and consistency for your preference while cooking.
Grinding frozen/thawing tomatoes can be a first class bitch of a situation or nirvana for processing. There is a narrow window of "slushiness" that will work. Too much water content in juice tomatoes can foul the mill also. I run the seed/skin mix through the mill a second time and usually get near a quart more juice. I like the pulp.

I have 6 16qt dish pans, 3 16qt stock pots that I use for the basic processing. A couple of ice cream pails for waste and at least 3 towels to mop up.

I use the food mill to make apple and pear sauce as well, after steam extracting the juice. I'm welcome to harvest the fruit from my immediate neighbors. This year's potential is 50 bushel apple and 80 bushel pear. Ready for stage two!