Dick is right
When I bought my Catilina 22, it had a bunch of blisters and I decided to fix them myself. Now that I have done it once I understand why it is so expensive to pay someone to do it for you; it is a real pain. Punch them out, dry for a month, sand, epoxy filler, barrier coat (multiple coats), and then bottom paint. You have to really watch what products you are using for each individual step because they are not all compatible. All in all, I've done it once, know how to do it, and know that it is worth paying somebody to do it for you. If your friend wants to do it himself, then West Marine's catalog has all the stuff and does a very good job of explaining how to do it. I just pulled my boat out last week after 2 and a half years in the water and the hull was without a single blister. To make a long story short, if you are going to do it then do it right; if you don't whole lot of your time taken up then get it done professionally. Best of luck!