Hi mk1978, a CAD program like MoI is focused mostly on precision type shapes and not organic shapes so it's not really the best tool for that type of work.

Probably the easiest tool for that type of work would be a displacement brush based program like 3D Coat or ZBrush, those allow you to raise or lower areas using brush strokes on the surface. Those work very well for sculpting on subtle raised or lowered details.

Maybe one related technique you could try in MoI is discussed here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=7516.3
http://moi3d.com/forum/index.php?webtag=MOI&msg=7516.13

- Michael