If you're using sythetic handle material (Micarta, G10, etc)heres something that I did in my early years....
Get the handle to about 95% shaped and finished.....then take a small drill bit (way back, I did it with a 3/32" bit and a hand drill), "Dimple" the entire surface, being careful not to go too deep. Then finish the handle with whatever your final grit will be. Its kind of a crude method, but it will be FAR better then the JB weld thing. The whole "trick" to doing this is to have the handle to the point that after you "dimple" it, all thats left is a VERY light cleanup with your final grit.