Oooh, one of my favourite topics. Chris is definitely right in recommending that there be no grit/distortion/breathiness in a belted sound. The twang is a crucial component, although I wouldn’t recommend nasality for belting. It gets the student to over-associate belting with nasality, which will lead to confusion in the long run.
I’m a big fan of using a good deal of thyroid tilt in a belt to make it safer. It thins the folds, demanding less power while also increasing note accuracy. It’s a kind of magically easy way of making notes easier – a proper Yoda move.
And it can still sound crazy awesome.