I find F360 and Rhino more useful for mechanical design or for geometric patterns, for these more organic sculptures, MeshMixer, Blender or Sculptris. For just a little bit of face modification, I think I’d try Sculptris first. The clay metophor is probably right.
After mucking about getting it into a 3D printable form or sliced for cutting is tricky though. F360, for example doesn’t like handling very many polygons which this model is very likely to have. Each of the software packages have model simplification methods (Blender has decimate for example) and then there are various fixers to make it hold water: https://www.shapeways.com/tutorials/how_to_use_meshlab_and_netfabb