Using Alpha with tessalation

While reading with high interest those fantastic tutorials made by Unreal and folks.

My question is about tessalation.

Read about adding snow.

But instead of snow, would replace it by moss, Thus providing a nice 3d and realistic finish on brick decayed walls. My plan is build decayed maps for a sniping and camping environment.

So my question is about if I use the alpha picture of a brick wall, and plug in the moss through it, and also using a very small brush so I could spread it in certain areas in a realistic fashion.
Like spreading grass in a map, but spreading verticaly on a wall.

Idealy, my plan would be a multilayer brick, where the first layer is brick it self, then second layer would be burned areas near the windows, then finishing with moss between the bricks , where the cement is.

My guess, burned ares would be better by using decals. hmmm.

I’ll be downloading the engine in a few days, unless version number is available now.