What is the best paint or coating to use on a patterning plate to indicate pellet strikes. It must be something useable very quickly after it is applied, so as not to delay shooting. I've heard of using whitewash, or some mixtue with oil in it. I've seen a fairly oily gray mixture used at the Perazzi factory in Italy. Any suggestions from you gun-fitters out there? There must be a traditional method.

I'm not talking about using paper sheets to view distribution or pattern percentage counting.