Yes, glass bedding a rifle IS a DIY project. I've glass bedded a couple of rifles myself that turned out just fine. I bed the action and a couple of inches of barrel just ahead of the action. (I don't bed the back of the tang; I just want the recoil lug taking up the recoil, not the back of the tang.)
In the case of a .375 H&H that had a secondary recoil lug on the barrel about 6" ahead of the action, I bedded the barrel up to and including that point. In order for the barrel lug to take most of the recoil, I used 1 layer of Scotch tape on the action lug (covered with release compound, and removed afterwards) so the front lug would bear just a
little more than the action lug. Couple of hundred shots later it seems to have worked well.
snakeman said:
As far as floating your barrel goes it's real easy just get a dowel that's slightly larger in diameter than your barrel and wrap it in sandpaper and sand out the barrel channel with it. It takes a little while but leaves the channel uniformly floated.
Most barrels have taper, so this doesn't always work. I prefer to put some duct tape (2 layers works well) on the barrel instead. I then sand out the channel by sliding coarse sandpaper back and forth along the length of the barrel channel (between the barrel and forend) while I progressively tighten the action screws. (Use care along the edges of the barrel channel so you don't round them over.) Once it's locked down, I have the room I need, but I still roughen the channel up a bit more with a Dremel.
I glass bed with the duct tape in place - except for the 2" or so of barrel closest to the action. But you MUST repeat MUST cover any tape you use as well as any metal that even MIGHT come in contact with the Acraglass with release compound! And mask the wood with masking tape, as some Acraglass WILL ooze out all over if you're doing it right.
Edited to add: I use mostly Acraglas Gel, around the action, and I add a little finely powdered metal to it, which improves the appearance and strengthens it. I've used regular Acraglas to do the barrel channel, but I imagine gel would have worked as well.