Loosely based on the Ball Canning book, and run past the canning expert at the Penn State Extension office, who used to HAVE the Ball Canning book contract (but now someone else does).
(My Ball blue book says 2.25 lbs of dried beans to a quart, but that's total nonsense--I do 5 lbs at a time and I get 9 quarts out of that.)
Anyway, don't do 5 lbs, do 4 lbs--that'll get you about 7 quarts and you can do the whole thing in one load through the pressure canner, assuming you're using a big/tall pressure canner, which you really do need to pull this off. Like one of the 23 qt sizes.
So the afternoon before canning, you rinse the beans really well and fish out anything nonedible. Put them in a large pot (even the canning pot is fine) and cover them well with cold water. Let stand 12 to 18 hours in a cool place (or the kitchen counter, if that's all you've got). Drain. (If it wasn't too cool and there's lots of bubbles on top of the water, maybe rinse and drain a few times.) Put in a large pot and cover with two inches of water. Chop up 3 or 4 LARGE onions and put them in a food processor so they're well diced (I like the sweet varieties for this). Add that to the pot. Add some spices. Honestly, pinto beans suck up flavor like cardboard, so you'd be hard pressed to over season the things. Black turtle beans have some actual flavor of their own, so go a little easier, but with pinto beans I pull out the Sam's club sized seasoning and give a couple big shakes of the "Mexican Pepper Variety" or "9-pepper blend" or something else that normally you wouldn't consider for a meal with the kids. Don't add salt though.
Bring to a boil and cook for 30 minutes (I tend to lose track of time during this stage though and so this is really more like, cook for at least 30 minutes--anything after that won't really hurt). In the meantime, get your jars and lids ready. Put hot beans (and cooked onion and seasonings) in hot (quart) jars, leaving 1-inch headspace. NOW add 1/2 tsp salt to each jar (Ball says 1 tsp, but that's actually more salt than I like in my beans, and I'm a girl who'll eat pasta just to have something to put butter and salt on), wipe off the top of the jars, put your lids and rims in place, tighten them up nicely, put in the boiling pressure canner (you only need 2-3 inches of water though) and after all your jars are in the canner, put the lid on the canner.
Let the steam build up without the weight in place for about ten minutes, then add the weight. Keep an eye on the pressure gauge. Stabilize the pressure at 10 lbs. As soon as you're at 10 lbs, start timing-- the quarts need to stay there at 10 lbs for 1 hour and 30 minutes. After the timer goes off, just turn off the heat and let it return to 0 lbs pressure on its own in its own good time. Don't try to rush it. Rushing around pressure canners means someone gets hurt in my experience (thus far it has been ME burning part of the flesh off my arm, not any of the kids, but just to be safe, I bark and fuss very loudly at the kids that they are to stay OUT of the kitchen when the lid is on the pressure canner).
Once you're at 0 lbs (I promise that thing is still hot as heck and is ready to give you a good steam burn, so take off the weight FIRST, wear oven mitts, and lift the lid so that it points away from your face and be ready with a place to put the lid down). Let the jars sit there in the pot another five minutes, then pull them out and put them some place where no baby or kid can touch them. Leave them alone for 24 hours (they'll probably sit there on your shelf and continue to boil internally for another 10 minutes, honestly), then unscrew the rims, clean the jars if you need to, label, and put on shelf.
When you're ready to eat them, if the recipe calls for them whole, you don't do anything but reheat (if the recipe calls for it). If you prefer your beans refried, spoon them into the food processor, process till smooth, then scrape into a frying pan to reheat (use a non-stick pan and you don't actually need any oil or anything. They'll be nonfat, totally smooth like store-bought, and maybe there's still some nutrition in there since you're pureeing them in the water they cooked in.
The end results is smooth and tasty and (we find) not as prone to give you gas as the usual method of cooking them in an open pot (which doesn't cook them as well as the high temps in the pressure canner/cooker).