Just to be entirely clear, this is the correct material to get for tanks - K&S #254 "Easy Solder" Tin, .008". It used to be labelled .007, now it's .008 but its the same thing.
It is NOT actual sheet tin (i.e. the element Tin (Sn) or any alloy of tin). It is mild sheet steel that is plated with tin for easy soldering. The normal sheets you see in a hobby shop are 4"x10", it is also available in 6" x 12" (K&S stock number 16254). The 4x10 will generally require two pieces to make a typical 6-9 ounce tank. I actually prefer making them in two pieces, since it allows you to adjust them so it is exactly square, but you can usually make a 5.9" or so long tank with the 6" material in one piece.
This material cuts very easily and cleanly with my stainless-steel Fiskars office scissors, with very little distortion compared to tin snips.
Solder with 60/40 or 63/37 *rosin core* solder, I prefer .040 diameter. If you think you need extra flux, I suggest Nokorode paste flux. I use a 260/220 watt Weller soldering gun, because it can heat up quickly, has very little tip mass, so you can solder one part of it without as much issue with unsoldering it where you don't want it. I have used everything from a 600 watt American Beauty industrial soldering iron to 15 watt pencil iron I got at a convenience store successfully, but the Weller gun is the best overall. The solder needs to be hot to the point of flowing like water, and the resulting hardened solder should form concave fillets. Blobs, balls, etc, are defects and are not acceptable, it doesn't take much solder at all, and putting on more than enough to form tight fillets between the parts is at best pointless, but probably marginally detrimental (since it stiffens up the joint locally, so it is more prone to cracking).
Do NOT use a torch of any type! Yes, it can be done but leaves no room for error.
Do NOT use StaBrite, particularly the flux! The marginal extra strength is not necessary if you get everything else right. If you want something stronger than 60/40, you can get Rosin Core Silver-bearing solder (which is NOT "silver solder") which is actually the same thing as far as solder goes, with a safe flux, and at least that will not corrode everything it touches forever. The StaBrite flux is extremely aggressive, the strongest and most persistent acid flux I have ever seen. This is great to solder difficult materials (like *chrome*) but it will very rapidly corrode anything you might make a tank with, and more-or-less cannot be neutralized. That sort of aggressive cleaning is patently unnecessary. If you have StaBrite solder, you can use that, but use Nokorode flux instead of the StaBrite.
Do NOT "rough up", sand, etc the tin plate on the K&S tin sheets, it is not necessary and will make it harder, not easier, to solder.
Brett
p.s. If you have the StaBrite kit, keep the plastic tube it come in, and keep the cap on it. If you just store the bottle by itself in a metal toolbox, just the fumes will corrode the inside of the toolbox and the tools. It even manages to corrode the solder itself, which is largely silver and tin! Ferrous metal doesn't have a chance. It's great stuff for non-structural connections to difficult materials like stainless steel and chrome (it will even work on nichrome wire, although the melting point is too low for most nichrome applications), but it's far too aggressive for general use.