I have found that small carbide bits work best on dremmels when doing precise work on these cars. The carbide will not chatter, and it gets warm enough to actually melt the plastic while cutting.

Safety
 

I'm 45 now. (Don't ask me how I got to this age. I don't really know!)
I have been using a Dremel tool since I was 9. External speed regulators are cheap second hand.
I always understood about the face vs disk fight. The face always loses. When I was 17 I was modding a CB case and a disk shattered. My face was cool but I had to give my leg 3 stitches. No I didn't feel the cut. This was back in 1978 and the laws were very different. Today I would have had at least a $1000 hospital bill and problematic parential concerns.
Only use grinding disks if you can keep most of your body safe.

The fibre reinforced ones cost more initially, and they can still shatter but they are much cheaper in the long run.

I just got diamond cutting wheels. I'll be testing one of them. An entire SWAT team won't have as much person protection as I'll have. I'm too old to get crippled!
BAE