A bottle of TruOil will do a BUNCH of guitars, unless you are putting on a finish deep enough to dive into. As far as I know, it only comes in one size - I buy it at the gun shop. It does come in a couple colors, but I just buy the clear (it looks amber straight out of the bottle). Mahogany will soak up a lot of finish unless you fill the grain. Also - if you want a smooth finish, grain filling is required - except for maple. If you don't use grain filler, your finish will look like many of the popular satin finishes that show the pores of the wood. Even Gibson skips the grain filling on some low end guitars.