This may be less useful now that so many of us are using CMC's, but Vivian Kistler pointed out to me years ago that a used matcutter blade is still perfectly sharp in the middle. Conveniently, this is the best part of the blade to use for trimming paper exactly to the edge of the frame.
If you lap a half inch over one side, you can make a perpendicular cut to the edge of the rail, then proceed to cut around the edges for a perfect finish. It takes a few tries to establish the technique. Now that I rarely use the straight line cutter, I still have a stock of blades and have continued to use this technique.
You can get "hand-held" ATG that is reverse-rolled to make it easier to use without a gun. This gives you much more control.
Jim Miller is right, glue is the least expensive and most secure method for applying paper. When I was working alone, I usually used this method. Now that I have employees, I try to keep things that create potential risk of accident out of the assembly room, so we use ATG for most regular work. It really doesn't hold as well over time though. For conservation work, I use glue and do the work myself.