In a word....DON'T!
If you boat is gel now, leave it alone. Automotive clear over your gelcoat will not hold up. Keep it out of the sun as much as possible, and keep a quality wax free polish on it, preferably something with UV inhibitors, and you will be happier down the road.
PS, just wondering why you buffed and glazed it if you were going to try to clear it anyways...?