Do you have speeds on your rotary tool? Sounds like you make be going too fast and maybe using a too aggressive bit. I like using a slow speed with a finer bit. An Exacto knife works good to clean up any extra dangling plastic along with a super fine bit for smoothing the rough edges.
![[Image: 7071.gif]](https://www.allsmileys.com/files/sweetim-texticons/7071.gif)