Well, anything involving balancing a weight over my head is scary, I find. *g*

But start with a really light weight, or no weight at all (I've heard some people suggest starting by balancing a shoe on the palm of your hand) while you learn the stages of the movement. Then you can up the weight gradually.

TGUs really work all the little stabilizing muscles in the shoulders, and for me they've been brilliant at building my confidence for doing skilled and scary things with weights.