Deformation: Use the pencil, not the pen

Getting used to the Deformation tool is important. This is an incredibly powerful animation tool which is also one of the more complex. I was having a lot of trouble with artifacts in my joints until I figured out: Outlines need to be done in PENCIL, not pen. My usual tool has been the pen. Big mistake. When I redrew my characters with the pencil outline, everything was fixed.

Thanks!