One thing you can do is not feed him mice (don't give in!) it is hard, they can go a LONG time without food (make sure he has plenty of water though)
try braining, take a f/t rat and poke a hole so brains come out
brown bag it

put rat and snake in a brown bag overnight (maybe put a brick on the "closed" end or staple it *no tape*)
try brown bagging it with a brained f/t rat
try a freshly thawed rat and dip the HEAD (only) in the HOTTEST tap water possible and swing it or drag it infront of the snake.
try feeding at night with a flash light.
leave the f/t rat in over night (discard immediatly in the morning if still there)
wait him out

it can take some time.
if you notice him drasticly losing weight (like within one week) then something else may be wrong
rub a f/t rat against a live (probably pee'ing everywhere) mouse, or let thaw out in SOILED mouse bedding
I'm a bit rusty, so that is all I can remember right now....lol But I'm sure others will have more ideas, they've been at it longer.
Oh and let one week go after each feeding, feed attempt free (like don't attempt to feed for one week after, I usually didn't attempt to feed again for 2 wks*14days*)
and like I said, don't lose patience. lol