Rolling fender lips...

[Y-TRY]

What's the best way to roll rear lips on a '68? I remember seeing a cool tool for it a while back.

What pointers do you guys have?

How difficult is it to do right / How easy is it to do wrong?

Can I also cut the trim pieces and roll them as well? I need a bit more clearance at the lip and may even have to take the wheels out slightly, as it rubs the inner wheel well under cornering.