a. Have a good supply of water on hand
b. Use non-ionic detergent (Photo-Flo by Kodak is the recommended one)
It takes ¼ oz in 5 qts of water.
c. Nylon brushes can be used as well as firm toothbrushes
d. Have a supply of sponges on hand
e. Plastic scrapers, which come in a variety of types, those used in
the kitchen, or for applying wall spackle etc.
f. Wooden picks, such as toothpicks or shishkabob skewers.
Note: I was told that a block of Styrofoam will clean off moss and soil
debris from old tombstones and will not damage the stone? I have not
tried it.