Just how badly blistered and abraded could his hands get? The worse he's injured, the better for my nefarious purposes. If the ground were partially frozen or something, would it be reasonable for his hands to be bleeding? He's in reasonable physical condition, in his thirties, and his hands are quite callused from playing guitar, although probably not in the right places to be of much assistance. (And, as this is fanfiction, it is canonical that he has managed to successfully rob a grave in the past, apparently without much difficulty, but I want to make this more difficult.)
Also, how long do you think it would take for him to finish digging? And how big would the hole have to be for him to open the coffin and get his poor buried-alive friend out? I just can't quite figure out the logistics of that.
Searched "digging blisters", "grave digging", "grave digging blisters", "graverobbing"...
EDIT: Whoa! You've all been incredibly informative. Thanks, everyone! I've kind of had writer's block with this story for a while, but I think your help might be the motivation I needed to get writing.
So, ix-nay on the frozen ground, then? I only really thought that made sense because fiction has misled me into thinking that just anyone can go around robbing graves and it's a walk in the park. So, not so much with that then.