Hi, how can I paint on a Terrainskin in RealTime?
Could anybody tell me a possible solution? Or even a snippet?

Thanks for advice.

Nobody knows? It's important to me because I dont like the other ways creating the blendmap for a shader.

You can paint on a terrain in real time, but it takes time to develop such a script, since it is not the easiest thing to do.
there are people who have made shadow mappers for terrain, which works in a similar way.

here is a link to a terrain shadow mapper I made some time ago, it could help you out