Okay iv'e done some assist feeding i would not recommend force feeding while he has an RI, only because i'm sure he is under enough stress from the RI, and stuff.
The only thing about assist feeding is that iv'e had snakes that would just never eat the rat that i assist fed it.
No matter how many times i would try to assist feed it, it wouldn't take the rat at all.
But theres no harm in trying.
Just make sure you wait 5-7 days after each attempt, because a un-succesful assist feed is really stressful to the snake.
Goodluck,
Mike H.