You know...
If you do not have a huge amount of fairing to do, and are only looking to fill a localized area, you can use Z-spar Splash Zone. Don't use it on anything you aren't going to paint, as the water drippage is a permanent splashzone-colored stain. Does not cake-frost with a spreader lika fairing compound...you sort of squidge it in with wet fingers. Boat Building with play-doh. It does have considerable durability, and it is very sculptable, which can come in handy. also shapes, files, sands very nicely.

Not exactly the stuff for getting rid of little ripples, but there are some times and places that it really is trick stuff.

Dave