The nice thing about the kits such as Acra Glas is their convenient size and of course they also come with most of the materials you need to do a couple of rifles.
If you are planning on doing several rifles over a relatively short time than go to Canadian Tire or some other place like NAPA/LORDCO/boat repair facility and purchase the resin/hardner you need in larger quantities. You can make your own flock with a small piece of fiberglass cloth. Some automotive supply stores also sell kits that are similar to Acra Glas but of course larger.
There are many other substitutes for fiberglass bedding material. Some folks use JB Weld with good results and others use the very expensive Titanium Putty or its cheaper counterparts.
Just about any of these epoxy mixtures will do a good job if they are mixed and applied properly.
Depending on your rifle's receiver design and its chambering you may need to help things out by also installing a cross bolt or recoil bar to aid the epoxy.
Last summer a fellow came to me with a lovely custom 98 Mauser. It had been his father's pride and joy and was built by an old friend of mine, Les Viel of Vernon. Les passed on many years ago.
The stock was originally a Fajen 90% finished/inletted model with the typical for the time exaggerated pistol grip and very high Monte Carlo comb. There were also some inlays of different colored wood and what may or may not have been ivory. The rifle had both iron sights and a 2X Balvar scope on Balvar mounts. Great looking classic styled rifle from the early sixties. It was chambered in the 458 Win Mag which is brutal on both the shooter and the beast on either end.
The only thing that saved this stock after 30 years of languishing in storage was the cross bolt that was fitted in the stock for the recoil lug to rest against and stop splitting. Sometime in the rifle's history, even though the inletting was excellent the rifle had been glass bedded. What was unusual about this bedding is that cloth had been used instead of flock for strength.
The rifle was brought to me because the best it would shoot at 50 yards was around six inches with the old hand loads they had.
The first thing that came to notice was that the action was loose in the stock. The front receiver screw was bottomed out and the rear screw couldn't be tightened any more without impeding bolt travel. The owner of the rifle stated he hadn't touched anything. We took it apart and it was obvious that the front screw had been taken off and tightened fairly often and in doing so compressed the wood. The rear screw spacer was missing. Obviously this rifle, even though it was glass bedded had a habit of loosening up in the stock.
What we found when we started to chisel out the glass bedding is that it was not hard but quite soft. After this many years hard to say why this was the case but I have rifles that are much older that are glass bedded and the bedding is still very hard. I suspect the quality of the glass or maybe the use of cloth rather than flock had something to do with it, or just an improper mix ratio.
We cleaned out the receiver area and the first four inches of the barrel channel completely. Added a new piece of wood under the front cross piece down to the trigger guard frame and included a front and rear spacer. Then we used a RED Titanium Putty kit to bed the action into the stock. Expensive, yes but the owner felt he wanted more strength than the fiberglass epoxies give.
To shorten this up, after a week of curing which is more than necessary, we pulled the action out of the stock and cleaned up all of the release agent (furniture paste wax) and put it all back together with proper torque settings. I was a bit leery about the old Balvar scope and mounts but they were just fine. I wouldn't shoot the rifle because I detest heavy recoil. It's just to painful. The rifle put its first three rounds into about a 1.5in group at 50 yards. Not bad for this cartridge but not good enough. Retorqued the receiver screws and put three more onto the target and this time the group was about half that size with two bullets cutting their holes. The next three were at 100 yds and the group was sub 2 inches. Not to shabby for 500grain bullets.
The rifle now has a couple of hundred rounds through it albeit with lighter 350-400 grain jacketed bullets. The receiver hasn't loosened and it hasn't lost accuracy.
This was rather extended but the point is, there are a lot of different products out there. You need to evaluate what is needed for your particular job.
I haven't noticed one bit of difference between the RED BOX Acra Glas epoxy from the epoxy I picked up at the boat yard. I have tried the Green Box Acra Glas twice and threw the remaining components out. Both jobs didn't harden properly IMHO even though I followed the mixing instructions perfectly. You may have different results.