Camels hair paint brush. They are generally very soft, but will do the job nicely with a little patience. It is what I have used except for the very most stubborn of hardened deposits. 90% of the deposits will come off with the brush without any damage to the finish. Some are a little stiffer than others in the shaft part of the bristles, but the ends are soft. That's what you are looking for. My brush is about 2 inches wide. Good hunting!