Anything that was on body color paint, glass, or smooth plastic, was able to get scrubbed off. But the textured stuff, (rockers, side moldings, underside of the bumpers, wheel wells) was pretty much set. I may try some acetone on a rag, with the moldings, and if that works well without killing my back, may do the rockers too. After I got done, I got around to the back and saw there was spray and fine particles all over the lift gate and glass
I have something similar that might be helpful, later in this post... (there's a 'tl; dr' there, for the impatient)
Yesterday, I finished the Accord's painting portion of the fenderwell repairs.
Although I had masked off the immediate surrounding areas, and was careful about where I aimed the rattle cans, I found out that I did have some overspray (not 'color' overspray; I'll call it 'particle overspray' -- you could feel the difference on the body areas -- it was rough feeling, vs. the clearcoat on the rest of the body. And I had left things to dry for a good long time between coats of primer > color > clear.
Thinking that I screwed up royally, I started looking for what to use to remove it.
One of my favorite solvents is acetone. Yes, it's listed as a good substance to fix overspray (although I'd probably test in as inconspicuous an area as I could manage, before going whole hog).
Another thing mentioned was paint thinner. I didn't want to try this, so discarded that idea.
I figured I'd start with something even more benign (?) than acetone, and at hand... brake cleaner.
Took a clean blue Scott towel, applied the brake cleaner to it, and wiped a small area. Came right off. It did leave a little white residue, but that cleaned right up as well.
Long story short, I was able to get all of my overspray off with brakleen, changing to a clean side of the towel for every new area. Most was on the rear quarter / factory clearcoat, although I did have some on the D/S rear window glass as well (I had a black trim piece on the window that also had some rust, where previous owner had done a sh!t job covering it up). Got that overspray off, too.
My lower rocker has that textured (pebbled?) finish on it, too -- in the old days, GM named that 'plastisol' (and it rode all the way up to the plastic belt trim pieces on my '86 Sunbird... so way past the rockers). Anyway, I didn't have much overspray on the Accord's rockers, but I did go over them as well, with no ill effects.
Took the Accord out to a DIY carwash with the high pressure wand. After a quick suds / rinse... all is well!
I won't post pics here, as I wasn't able to get the outer fenderwell area on the D/S perfect (as I knew would be the case). But all in all... I'm pretty happy with the finished results (and I'm really picky, as most of you know). I'd call it a good '10 footer' result, if I were judging it. And the inner fenderwell lips (both the 'bad' D/S and the 'not so bad' P/S) look really good, IMHO. My eye was always drawn to the rear fenderwell rust -- now it looks pretty close to the way it rolled out of the factory back in 2008. As I said earlier... for a first attempt at real bodywork... I can't complain. Hopefully, it lasts awhile.
I decided to go with matte clear on the inner fenderwell lips; in retrospect, a satin or even a gloss clear might have been a better choice. But that's easily correctable, if I want to redo it later.
TL; DR: Acetone
should work a treat. But brake cleaner also might. Another substance is 'Goof Off' - I've had great results with that in the past, although it does leave an oily residue behind (along with a bit of an odor).
PS: (for Blckshdw) For the inner wells, Rustoleum does make a matte 'bumper and trim' black, which I used for the side window trim piece on the Accord. A word of warning... it spatters easily. You can wipe it off with water, but you need to be quick about it. Also, even though it's listed as matte, it was a little shinier than I'd prefer, when looking at the passenger side (factory).