Marine Tex is being used by many top smiths, it seems to be the "in" bedding compound these days. It is relatively easy to use, but very unforgiving if you screw-up. Not effected by solvents, won't get punky. Brownells sells it. I have also used Devcon with nice results.
No doubt the Brownells bedding compounds (they have three or four proprietory names) are very good. They also have a spray release agent that I have used many times. Some guys just use Johnson paste wax, it spreads nicely and works fine.\
Interesting note re bedding. The MASTER bedding specialist at McMillan full length beds stocks, from the tang to the fore-end. Not sure this is necessary on heavy stocks but I recently watched a slide show explaining roughly how he does his magic. This guy is a craftsman, not sure what his name is but he is acknowledged as being "the man". His bedding is absolute, pure perfection - that is why they can charge the big bucks, it is worth every penny.
Just my thoughts - wish I could do work like that...
A simple, readily available and inexpensive solution can be found at almost any hardware store. It comes in a syringe with two tubes attached together and has names like Epoxy steel (epoxy must have a metal component to be effective). Made by companies like Devcon, Lepages this stuff works very well. Nice and thick so easy to work with and does not run. As good or better then any "gunsmith" type product.
I use liquid PVA found at plastic shops. This is a mold release product used in fiberglass mold lay ups. Works very well and can be removed with water. In fact, this is what allows very tight beddings to be made.
The guy who does all the bedding for us is John Hanlon. We like to think he is as good as there is. The reason we bed the entire length of the forend is strictly for cosmetics. It allows you to get a uniform space between the stock and the barrel including the different contour changes. We tape the barrels with 30 mil pipe tape for hunting rifles and two layers for tactical or competition barrels. It gives a nice smooth finish with plenty of free-float.
As for materials. My father used to swear by Duro Steel filled Epoxy. But when they added concrete to the mix in about 1985 it changed the dynamics and it became unsuitable for bedding. A friend in the boating industry suggested we try Marine-Tex, which is a steel filled epoxy used to patch holes in engine blocks and such. We tried it and found that it was the best thing available so we started using it exclusively. (Just one more thing the gun industry can thank Gale for) It is thixotropic so it won't run and sag during the bedding process, it sets in a couple of hours and cures overnight. It is pretty much impervious to most solvents especially if you don't let it pool. It comes in a dark gray or in white. Some like to add color to the white.
Just remember one thing. It's not an adhesive. Don't use it to glue stuff together. We had a bunch of butt-plates come loose at a National Championship match after laying out in the sun for a while. Couple of rounds down range and all that was holding them on were the screws.
As for any other bedding compound. Anything on the market will produce the results desired as long as the process is done properly. Whatever you use will work just fine.