Can you paint with a layer that was imported in with world comp or and a second mat to landscape

trying to add a laje bed to my mountian landscape used up my 16 texture ref so how to i add sand to a selected area can i make the weighted layer paintable or adda second material or mabe there is a way to increase the texture ref

i can import without using world comp and its all good nothing with it checked ive tried that and more no brush circle at all