Grinding

[JyonnyNovice]

I'd suggest starting to familiarise yourself with the skull. That method you're doing with the ball and the cross has some drawbacks, although it's a great place to start. Getting to know the skull better, and the interlocking pieces that make it up will give you another point of reference to see if your heads are on track or not. Skull Sketcher is a free 3D tool with a skull you can rotate all around. Good luck! Hands and feet looking good ^^