Wait until your character is at least somewhat leveled up. Plug in a second controller
and begin a co-op game without using a second profile. Using the second controller, go
to your henchman's abilities and discard all of them, returning the experience to the 
pool. Then quit out of the co-op game. You should find that all the "leftover" 
experience has been transfered to your hero. Repeat ad nauseum. *Note: Your co-op 
henchman will have the same abilities that you do, so the stronger the hero the more
abilities there are to sell off and thus more experience.