I am working on a Noble 6 Helmet with a friend of mine, and we are on the bondo/sanding stage. People suggest to use "spot putty" on sections to make it completely smooth. It was late in the day, too late to stop by the store again, so we looked around my friends garage for a suitable substitute. We found some drywall filler and applied some of that to the uneven sections as a test. After it dried, we sprayed a little paint on the area to bring out imperfections. We noticed that the paint looked noticeably different where we applied the drywall filler. So, my question is: Is it okay to use drywall filler rather than spot putty? (I don't remember the brand of the filler we used, but I can get it tomorrow if I have to.) Also, is it possible to avoid the odd look by simply using primer first, or using multiple coats of paint? If anyone needs more details, just let me know.