My recommendation is to spray on Feather Fill (by Evercoat) over what you have right now. You would obviously need a spray gun, but Feather Fill is essentially sprayable body filler--a polyester product that you put a little catalyst in. It adheres great to bare metal and body putty, and it sands out easily with block or long board, wet or dry. I tend to use black so I can sight down the car and check the reflection for high and low spots (after sanding w/ 400), but if you're more proficient than I, you can get it in white, grey, or buff as well. You can keep spraying over the same area to build it up ( a lot more build up than SEM's high build); you can thin it out with a little acetone for a smoother (less grainy) finish; and you can mix up a little in a cup and dab it on with a small brush if you find a very small flaw someplace. And you can sand it an hour after shooting it; sooner if you have it baking in the sun. Try it--you won't be disappointed.
