The problem with thymol is that it can yellow paper. I don't know if this is an immediate reaction, or more long term (probably the latter) as its use was going out of fashion when I started conservation in the mid '80's. Also, thymol will eventually evaporate from the paper so it is not a permanant solution.
Interesting aside - thymol is found in thyme, and also lysterine!
Eli, you can brush the loose mold off with a soft brush, and maybe even clean by gently rubbing (gently is the important thing) with grated art gum eraser. If the client doesn't mind how any residual staining looks, that's great, just leave it alone.
The most important thing is to make sure the piece doesn't return to the same environmental conditions that caused the mold in the first place - high amibient relative humidity or water damage.
Rebecca