There are obviously many ways to get it done. A multi-offender taught me to use quart ziplock bags instead of caulk guns. Turn one inside out, weigh out a roughly golf ball size mix on the bag. Turn it right side out, squeeze out the air, and mix with a short piece of dowel or PVC pipe used like a roller. Roll the mix to one corner then push it back slightly. snip off about a 1/8" to 1/4" diagonal. Now you have a baker's cake decorator bag. Very easy to get into tight spots. On interior ribs, a donut around each rivet and the drop in each rivet hole (and over the shop head, for insurance) does all the sealing. Any additional sealant on the rest of the faying surface and/or edges is just lost payload.
On quantity vs leaks:
I built 2 ea -7 tanks, and 2 ea 3-bay leading edge aux tanks, with *one* can of sealant from Van. On the two main tanks, I had exactly one leaking rivet (probably near the end of a session on a bad day). The auxes had some back baffle leaks but those were purely my fault due to running the trailing edge beads too far forward on the skins (spar has a bigger radius than the tank back baffle).
Not the most fun part of the build, but orders of magnitude better than the massive quantity of wasted time searching for parts using that pick list who's order was created by a random number generator.