Assisting is fairly easy if the snake cooperates and does the rest of the job if not it's no longer assisting but forcing which is not much more difficult but not something I would consider doing unless really necessary.
The difference is that with assisting you open the snake's mouth slightly and push the prey in it and let the snake do the rest, with force feeding you push the prey all the way and then massage the snake gently to make the prey go down it’s belly.