I have installed a few sets, and have had success using a padded vice and a drill press. I square up the butt stock in the vice, using a square placed on the drill press table for a visual reference. Start with a 1/16" bit and work up to the desired hole size.
I see you have the B-Square kit. I have no experience with that kit, but from the looks of it, it should work nicely. My concern would be how to keep the plastic guide square with the butt stock. I think I would chuck the stock into the cleaning vice, use a square to make sure it is straight up and down, and Duct Tape the guide to the stock. If you are not confident that the plastic guide is "secure enough" to the stock, by all means try something else! Take it nice and easy.
Good Luck! NailGun
