I got a comment on a local forum about the Liquitex Stucco that I use on my bases, so here you go...Here is what it looks like when wet, I just spread it around the base not trying to keeping it level, the rougher the better.
Here is what it looks like when it dries, I use this stuff on everything, here I use it on one of the GW "Creepy" trees GW has out.
Here is another shot unpainted on Gimils base.
Here is the same base painted and flocked.
Here are few other shots...