solution heavy duty, minitex with tampico attachment, thorough rinse. Reduces it vastly but I've yet to get a 100% result. Customers are always more than happy though, as I tend to under-promise a little bit to be on the safe side.
I probably convert 3 out of 4 quotes for these types of jobs, as there's always one who doesn't want to pay if it isn't going to be perfect.