Re: Gluing keypads
I've been overhauling saxes for over 40 years and never used flake shellac, so I can't help you there. I use stick shellac for small fast jobs, but when doing major pad work I use a glue gun. There are several things I like about it: First, it has a good melting point. Second, it has a long work time. Third, it doesn't expand when it heats and contract as it cools. Fourth, when shellac dries it's very very hard. When glue gun glue dries it has a "rubbery" consistency. I've found this helps to reduce the pad noise.
A general note on using any kind of glue: USE A LOT!!! There are several reasons for that, but most importantly you want to be able to float the pad. If you use a minimal amount of glue the only way to adjust the pad is by bending the whole cup. If the pad is floating on a layer of glue you can heat it and nudge the pad into position. When I'm asked to adjust a repair from another shop, it's almost impossible if there's not enough glue behind the pad. I've made minor adjustments on overhauls I did 5+ years ago, and if the pad is still in good condition it's possible to achieve a 100% seal simply by floating the pad back into position.
One other suggestion on the larger pads: use a razor blade to cut raditating lines in the cardboard backing, starting from the other edge towards the middle. Don't start in the middle and go to the edge because for sure you're going to cut through the side wall of the pad! Doing this makes the pad more flexible, which makes it easier to make fine adjustments when floating the pad.
Good luck with this! I'm a big proponent of do-it-yourselfers...when I was a kid in high school I took apart my Mark VI tenor...