I blocked my epoxy primed front fender and sanded through 3 or 4 high spots. Sprayed 3-4 coats of polysurfacer and blocked again, sanded back through the same spots again. They are about 1-2 inches in size. Not sure what to do. Its the top of a 67 mustang driver's side fender. I think maybe my durablocks may be too rigid for the contour? Should I add another 3 or so coats of polysurfacer and try a less rigid block? Should I just spot prime or spray the whole top of the fender? Also, I have been using a 3m no. 20 sanding sponge on the really contoured areas of the fender, is this ok? Thanks for any advice.