Hi Anis,

The Image below is a .obj from MOI3d imported into 3d-coat
The feather brush is made from an bitmap (in this case from artrage)
Export limitation off 3d-coat is .obj .lwo (so no STL)

I have also Silo3d which can export STL
I use it for organic modeling
For example a human hand is done i minutes(in MOi3D i am still figuring out)
Only minus of the program is the snapping features (and some bugs)