I am using Wall Spackle, yes wall Spackle. Phil Thomas suggests using it in his Sport 40 instructions and at first I though he was a little nutty. Come to find out the stuff works awesome and cut my paint prep time in half. Just make sure you buy the regular spackle and not the lite version. I covered my whole hull in the stuff and after it dried I used a red scotch brite pad to sand it ALL off. All that was left was just the spackle filling the pin holes. To prep I just used compressed air to get the dust off and then I wipe the hull with a dry towel. Don't use any water. When I prime the boat I spray a very light coat and let it dry followed by a heavy coat. Then paint the hull and its done. I did this with my Whiplash Cowl and it came out perfectly after two failed attempts using lite body filler that resulted in sanding more and adding more pinholes. The nice part about the Spackle is that you don't need anything more than a red scotch brite pad to reomve the extra spackly and you won't sand into the hull causing more pinholes.