I had never considered cleaning a tombstone. Using a very wide and soft, sable paint brush, I would "dust" the surface until I could remove as much dust and excess particles. I carry masking tape, acid free tracing paper and soft charcoal. I tape the tracing paper over what ever section cannot be read and do a rubbing. The masking tape removes easily and I have yet to have any residue left. This way I do not damage the stone, and am able to obtain the info I need. Tracing or rubbing has been used for decades and has proven to be the safest and easiest way to obtain info from the stones. Evelynne Guthrfie