You have to be really careful with paint. Those methods you mentioned are not very paint-safe. Nail polish remover may be OK, but I don't endorse it as I have not tried it and the chemicals may be strong enough to damage or remove your paint.
Paint safe methods include a diluted solution of alcohol (50/50), bug & tar remover (I'd suggest the BMW stuff), or claybar. Claybar may not be able to remove it all though, it has difficult picking up tar and other sticky substances.
For removal, use a quality microfibre towel.