I have used Acraglas, Acraglas Gel, Devcon SS and Al filled epoxies, Marine Tex and Bisonite. And I have used other epoxies but I cannot remember the names.
My epoxy use falls into two categories: stuff that needs to be poured, stuff that needs to be as thick as peanut butter.
I use two part epoxies and mix them in a Dixie cup.
Certain applications, like filling cracks, the glue needs to be as thick as warm butter. Acraglas works very well, and so has Everfix resin.
Both of these glues flow well, and the cured remainder left in the Dixie cup is very hard and very strong.
I really like the Devcon epoxies. Devcon 10270 Stainless Steel filled putty is as hard as glass, very strong, and as thick as peanut butter.
Bisonite is a curious epoxy. It pours well for maybe ten minutes, then it thickens to a peanut butter consistancy. It used to be very popular in bedding M1’s and M1a’s. It is red in color and rock hard. I recently used the stuff in bedding two M700's. Works as well as ever.
Champion’s Choice carries bisonite.
http://www.championshooters.com/bedding.htm
I have used a lot of Marine Tex, it cost less than most, as thick as peanut butter when mixed. I don’t think it is as hard or as strong as Devcon or Bisonite, but it is easy to get at a boating store.
Boating stores have an excellent selection of epoxies.
Let me mention a cheap release agent. One that I wipe on the outside of the stock, anything that gets touched as I put the action in stock, and that is Johnson Paste Wax. You can melt it and paint it on.
The spray release agents work best for the actual part of the action that you want to be in contact with the epoxy, and that you want zero clearances.