This past weekend I was attempting to refinish a handguard for my rifle with krylon grey primer and some foliage-green/oregano-ish colored rustoleum. It didn't end well. The krylon went on superbly, however the rustoleum was crap.. goopy, left little "pore" looking indentations as it dried and just generally looked like crap. So I took a cleaning toothbrush and the remainder of mineral spirits I had and an old pot and soaked the handguard while scrubbing it with the toothbrush, rinsing it in the sink and repeating that process for as long as it took to get most of it off. Unfortunately, theres still a bit of a residual greyish "dust" looking stuff (it looks like ash, but doesn't rub off on my finger when I touch it so it appears to be 'cured' onto the surface somewhat) left all over the anodizing. I haven't attempted to take it off yet, but I was going to just do soap/water and a toothbrush or some zep citrus degreaser + toothbrush and then put the grey primer on again and leave it like that. I liked the way the primer looked, so I might just settle, until I can get a foliage green durakote or something similar done.

Does anyone have any tips on getting this residue off?