A decent stripper should be fine. I use one called Carefree Speed stripper and just removed a bunch of oil from from slate with it the other day. If needed then steam is good but for me was a case of just leaving it to work, agitating a bit. Rinse and repeat.
The nice thing about granite is that you can hammer it with any chemical or pressure you want. I once removed limescale from granite with my pressure washer on the pencil jet setting, and it didnt effect the granite at all.