What slate, thinset, grout and sealer should I use

I have some very fine latex paint overspray and drips that I need to remove from my natural slate tiles in an entry Foyer. The paint is anywhere from 3 to 6 years old, and the slate was never sealed as it should have been after the original installation. How do I safely remove the latex paint overspray, and what is the best sealer to use after the paint removal. Also, is it safe to install slate tiles over a concrete slab outdoors in Colorado, where it gets below freezing all winter? What slate, thinset, grout and sealer should I use? Thank you for all your help. Can you e-mail an answer back to me?