I’ve used

interior spackeling compound, light weight patch to add a concrete texture to styrene.  Water could be used to make the texture finer.  

It might be worth an experiment.  I bought a container that was about a quart and also used it for some scenicing. 

You might get a flat surface using a plastic putty knife or dry wall tool.

Nick

We're talking how thick, and

We're talking how thick, and in what scale?

Honestly, even in O scale you're looking at probably only .060" added "thickness"... it's more just a texture, and not much of that, even.

What about building the structure (minus glazing), shooting it with a light coat of base color, dusting on talcum powder, while the paint is still wet, then finishing with the last of a coat of spray paint?

If you want to skip the talc, just paint it with a "dry" air brush to get that slightly "grainy" finish we usually try to avoid?\

Do they make

any of the special effects paints in spray cans that might work? A velvet type texture  perhaps? ..DaveB

HO scale and 1" thick or less

And I forgot about talc or texture spray. Thanks all.

The "stone effect" spray

The "stone effect" spray paints have a dappled texture... and multiple colors within... so overspray THAT with the color of your choice.