Another ditto to Bruce's post, and I will also add this:

Once you have turned the prop backwards, put the started to the spinner, and before turning the starter on, make sure that it is

1) aligned as straight as possible with the spinner

2) pressed FIRMLY against the spinner

But no matter what you do, it's bound to bite to sooner or later. Just walk up and down the flighline and look at everyone's plastic spinners. You'll see the same nasty little ring ground into 95% of them. (Only the very new ones will still be smooth)