Yes, finetuning his SpecularChannel with a Map would be great but I´m not sure how to do this. I painted the Diffuse and Bump inside of Sculptris and the UVs are cut into small pieces. So I couldn´t simply load a tileable Map into the SpecularChannel because of that UVs ... and painting Specular inside Sculptris isn´t possible ...

I guess thats why it´s freeware :-D