Been there, done that...
The easiest thing to do is to find a gen 18k bezel. Below is a picture of my WM9 TT. The gen bezel snapped right on. Interference that prevents turning is caused by the insert rubbing against the top of the retainer ring. Because I did not wish to trim my gen insert, I trimmed the retainer ring until the bezel turned. Eventually I found a gen retainer ring and fixed it properly. It's got a gen dial, gen crystal, gen crown/tube, Swiss ETA 2836-2, BK datewheel, gen retainer ring, gen 18k bezel, and a gen insert. All in all it's not bad for a fake watch, and makes a nice beater.
Good luck with your project,
JJ