Reply #78: Car guy here...

[Mopar151]

I use a Magic Eraser in the bathroom - they rule! Likely, the reason the paint came off so well is because of some residual wax and/or "dead" paint on the surface. Also, the paint on the car is fully "cured", and is much tougher than some cheap spray paint. If the paint on the noble steed is not too bad, some good cleaner/wax will make it look way better, and protect it, now that it has been prepared for paint to stick to it. Something like this:

Barry Meguiar is a nut - watch his "Car Crazy" show on Speed channel sometime (Dude looks like they use his own products to make him up!), but his family has made a full line of good polishes for years. Rubbing compound can be used to remove even cured paint (i.e. truck lettering), but you can remove paint all the way to metal with it if you go too far! Some kitchen cleansers are quite effective - my buddy's "secret" ( Davy has no secrets after 4 beers) paint prep techchnique involves Soft Scrub with bleach and a Scotch-Brite pad

Chemical weapons: If you ever have to go past the magic eraser - like for pine pitch or road tar - a mild Xlyene solvent, like Thin-X usually does it, as will kerosene. WD-40 contains some kerosene, but the light oils in it work really well on ADHESIVES - like tape or bumper sticker residue. I've seen WD-40 take off stuff lacquer thinner would'nt touch!
If that don't do it - you are entering nuclear option territory! Most of the solvents in this category are form the "ene" family - including tolulene, heptane, acetone, and various other clhorinated solvents. Carb cleaner is a tolulent/Xylene mix, brake cleaner is mostly Heptane.
Carb cleaner or lacquer thinner (tolulene, acetone, alcahol,xylene) will remove most uncured paints, and will attack cured paints somewhat. Brake cleaner is more agressive than that, as is straight Acetone.
I don't know what to say about the rainbow sticker - I see 'em all over NH and VT, but thugs are everywhere. Is there something a little more subtle? And he's "marked" in that neighborhood anyway, so get a coat or 2 of wax on that thing!