paint, rust, etc. Those things I know the prespray won't touch.
For paint I use a combination of Zep Orangel and Bridgepoint Alsolv, loosens it up nice then rinses away. I have nice scissors for those multiple paint spots about 1/4" in size right up by the wall where bad painters always leave them.
What's being used on rust?
I have TSR that I got from Les. Works really nice with a bit of agitation on the bigger spots. Used to use Prochems Rust Remover, liked it because it was a gel and would stay on the surface. I could treat it and walk away, it would be gone by the time I got back to that spot to rinse.