If you wait more than 12 hours you should, like he said scuff down with a Red scotch pad and reapply, then prime. You can apply it over paint or bondo but it is only effective on bare metal. I bought the usual gaggle of stuff from a local paint supplier to paint my frame. I had no need for a gallon of DP90 + gallon of Catalyst. When using epoxy primer it doesn't matter which goes first. I then use a primer sealer or epoxy primer to seal up the surface then apply the top coats. Some like S-W "Vinyl wash" clearly state DO NOT sand it. applying the next coat. Typically the next step is apply a primer surfacer, 2-3 coats then block sand with 320-grit. Your self etch primer should be just a really light piss coat, you don't want a thick coat, it could cause your top coats to crack over time. The Self Etch Primer is a good first step for bare metal, or an Epoxy Primer. Self-etching primers have to have another primer over the top of them or the paint won’t adhere. Hope this helps, Mark Allow more time at cooler temperatures. Do not use near open flame. Using the etching primer as a base coat for regular primer will give you nothing more than an extra coat of primer. For this reason, self-etching primers are not recommended over clear coat finishes or existing paint. Allow the final coat of Self Etching Primer to dry for a minimum of 3-4 hours before dry sandpaper. That etches into the metal and then the primer chemically bonds to it. Self etching only needs to be applied to Bare Aluminum. Dries to the touch in 10 minutes and to handle in 15-30 minutes. Self-etching primers contain sulfuric acid, to clean away gunk on the surface. Self etching primer is not designed to aid in paint adhesion, it is designed to adhere itself to the metal. Epoxy works pretty good over Acid etch as the epoxy does not tend to melt the etch like, say a 2k primer would, only issue will be is the etch is the weakest link but normally OK, if done this way. Once applied and dried (couple of hours) Use a 3m Scotch Brite pad to knock down any nibs and then shoot the Bare metal primer over the entire Prepped(Acetone wipe down) surface. At one time S-W's "regular" etch primer was actually called a "surfacing" etch primer and it would sand pretty well. Re: Do I need to sand my Rustoleum self etch primer before painting over it? Putting more of the primer won’t make it work better. But that was just nuts and you will not find any reference to … There is NO reason to sand etch. (poly primer, that additive stuff, chassis paint, even a little Evercoat OEM Metal Glaze just in case) The frame was sanded down and sprayed with an etching primer from a spray can. This helps remove sanding scratches and small surface defects. In the meantime, it’s important to talk to your paint dealer about the time window allowed between the primer and paint topcoat. The reason being that the acid/chemicals in the etch primer "could" be trapped under the filler and cause it to break down if the filler is applied over the etch primer. DRY & RECOAT Dry and recoat times are based on 70°F (21°C) and 50% relative humidity. It can’t be an epoxy primer, but it can be a urethane primer. Just make sure you shoot the first coat of epoxy with NO reducer, just 1:1 with activator. The self-etching primer is usually gray or olive drab gray but the color is just there to show you where you’ve put it on and it is very thin and one thin coat is enough. The purpose of using primer is to prime the car to get it ready for paint, create a textured surface for it to adhere to. Some are a few hours; others allow several days. When using etch primer the filler should go on to the bare metal first and then all is covered with etch primer. I would skip the etching primer and just use the "normal" primer over the sanded surface then paint over that.