Just finished up my second rattle can spray job, and I'm seeing the same problem -- lots of little (and a few not-so-little) rough bumps on the flat surfaces of the guitar. I sanded both guitars to 400 grit before painting and wiped each well with a tack cloth after hanging it for painting, so I don't believe it was caused by dust or foreign objects. I'm sure it's in my technique, or lack thereof. Any thoughts?