Is he willing to work hard at it, because in my experience stopping a flip takes a lot of work.
I used to play off 9 practising a lot and flipped the crap out of it. If my timing was on I hit it pretty solid but high and spinny. Spent about 18 months really working on it 2-3 nights a week at the range plus a round each weekend plus who knows how many balls around back yard, rehearsal swings and research time.
Anyhow, end result for me was that I now play of 5-6, never practice and play about once a month. Timing is a lot less important when the flip is less!
For me a few things helped.
I wrist tac-tic and some wooden dowels were the only training aids I used.
The tac-tic is self explanatory, the dowels used as per here
http://www.iseekgolf.com/golfinstruc...plane-part-one.
Start with chips, I used to even flip them, hit a chip shot and hold the finish and have a look at the left wrist. watch and learn until it is flat at the end of a basic chip. A big part of this is hitting down through the ball, take a divot, exaggerate it for effect when practicing. I spent a year taking massive divots on chips to get this down, not the best way to chip long term but it was part of learning for my full swing.
Then move up to a pitch, same thing.
Then look at a half swing....this is where I kept breaking down. You have to learn to roll the wrist, if you don't roll it has to bend. Again, observe what you do and you can teach yourself.
Finally you can get to a full swing. That progression is not going to be in one practice session, even if you are bloody good that takes time to work through and sink in.