i used the clear liquid epoxy from harbor freight, filled in and worked like a charm. that was two years ago, still solid and no cracks. did the lug, tang and everything inbetween. if you don't mind paying the money and wanna use what the pro's use, get some brownells steel-bed if only doing the lug. go with arca-glass resin if doing the whole stock.
check out iraqiveteran8888 on youtube for some great bedding videos. he has one where he only des the lug and tang and another that does entire glass bedding. good learning tool