You may find the link in my signature useful--there's a section about mouthpieces and one about cheeks.
For a brand-new greenie, I don't think 15 minutes is all that long. Give him time and just longe him while he's wearing the bit until he realizes that it's not going to hurt him and it's there to stay. Or bridle him with a halter underneath and leave him tied (but supervised) for awhile.
For a greenie, eggbutt cheeks are kind of nice. So are French link and mullen mouthpieces. For Western riders, a loose ring jointed snaffle is typically the starting bit of choice, but that's not always the best combination for a greenie....though people have been getting along just fine with that set-up for ages.