Is there any advantage to prepaint the rocks before fixing them to the plastercloth using hydrocal ? Some access for painting the rocks already in place might be limited ( like if the rock is in a trench ).
Are you talking about real rocks, or some you have cast up in a rock mold from plaster? With real rocks, I don't see any reason to paint them at all other than to paint the plaster to blend it in. With rock molds, generally you would color them after installation. The normal way to color rocks is with washes rather than paint, by spraying in a sort of "spot" pattern.
The rocks have been casted using Woodlans-Scenics rubber molds and hydrocal.
I already have some experience with them because I used those W.S. rocks in a diorama and painted them after installation , washing them ( as you suggested ) with a "leopard" pattern.
Now I'm ready to start the scenery on my "real" layout and thought that maybe it's easier to paint the rocks first, then glue them on the layout and blend them in the plastered cloth terrain with sculptamold.
It depends where they are going. Rock outcroppings that will be surrounded by vegitation it might be easyer to pre-stain. A big rock face you diffenently want to stain after instalation because there will be extra plaster added to smooth joints over. And just a tip I have found that Sculptamold and Hydrocal take the stain differently.
