Hi Gaston, MoI is not really the best tool for making faces like that.

The primary workflow for MoI is to draw some profile curves and then build surfaces from them.

For mechanical shapes this works really well, because for many mechanical shapes the 2D profile blueprint curves define the overall shape.

That does not work so easily with a face because a face has such a constantly changing nature to it that just a single profile curve does not define the overall shape of the face very well. Like for example a side profile would include the nose but it is not correct for the nose to traverse the entire face side-to-side, it's a small localized detail. Faces are full of these kinds of small localized bumps and details.

Sculptris like Pilou mentions is a really good idea to try - it's easy to use and its method of sculpting by applying brush strokes allows adding little bumps and small localized details well. It's just a better tool for faces than MoI.

- Michael