I just wait until they are plenty hungry. 7-14 days for adults. Then leave the rat in its box, nearby the snake for a little while, so the snake catches the scent. Then i open the enclosure and drop the rat in there as quickly as possible, so i dont get bit! My snakes eat thawed rats like clockwork, if i gave then live they would strike it before it hit the floor!
what are your temps? I had a snake fast on me, and it turned out the ambient temperature was too low. Now that i have their temps all perfect, they all eat like clockwork