featherfill 2g is supposedly really good, need a 1.8 tip or larger ( i would prefer a 2.0mm) VERY Thick STUFF, But does it's job good.
Featherfill I've tried featherfill and wasn't very impressed with it. Sprays rough even with a 2.0 tip, and sands horribly. I prefer using evercoat metal glaze to finish bodywork and a good 2K primer surfacer to fill scratches and featheredges. Nason makes a pretty good primer. Xtreme Paint- Newbee-Phils friend-(www.xtremepaintandbody.com)
With a urethane reducer? never tried that with that kind of primer, but I see you mentioned 2g (2nd generation?) not sure what mine was I used. I know it was called featherfill though. I threw it out. Just stick to pollyester putty for minor imperfections. Fast cure/easy sanding, done long before the polyester primer cures.