I BIAB now, previously I batch-sparged into an esky (uh, cooler) mash tun. You can do it, it's not overly technical, it just takes longer. I would recirculate until the wort runs clear/you're sick of recirculating, drain the whole batch into a fermenter (or anything with liquid markings on it), and then sparge with whatever amount you need to make up the boil volume. Refill that amount, stir, recirculate, drain, repeat if double-batch sparging, or boil.
The main benefit for me switching to BIAB was time. It knocked an hour + off my brew day straight away. I've been switching recipes a lot, finding my efficiency moves a lot depending on which type of grain I use, so establishing a reliable brewhouse efficiency has been difficult, but I did notice an improvement wholesale going BIAB. That could be put down to poor procedure with the mash-tun method, I don't know.Brews are potentially less clear, but that's something you can alter with whirlfloc/irish moss, and recently I've been tipping into the fermenter through a sanitised wheat bag, which cuts the trub in half.
I use a crab boiling pot. It's 38 litres (10 gal) and has a perforated aluminium pot that fits inside it which would usually hold crabs - very handy to strap the wheat bag into, making lifting a lot easier. The inner pot sits on top of the pot and drains. Currently I sparge by pouring water through the bag. No lautering or circulation involved. Or, use your old extract pot to teabag sparge. I'm sure that's the technical term...
I hot water sparge to save time - adding cold water to your boil pot increases the time needed to bring it to boil.
The limit is about 8kgs of grain - we could probably sneak that to 10 if I didn't use the inner pot. As long as you're paying attention as it comes onto boil, you can boil 9 gal in a 10 gal pot. That grain bill translates to about 1.050 for 6.5-7 gallons. I use 8 gallon fermenters, so for me it's a no brainer.
Prices in Australia are stupid (the pot cost $110 dollarydoos) but you could probably find one at a camping store stateside for less.
I haven't entered water chemistry yet. Sometimes I boil my sparge water the night before, let it cool, transfer the water, scrub the pot (to remove fallout) and boil away. The water definitely tastes cleaner at that point, but I think you'd need a more advanced tongue than mine to taste the difference in beer.