The cooler the covering, the better it seems to peel off without leaving any adhesive. work on it in an air conditioned room for the strip-down.
The knife scraping works for some people to get rid of what still sticks... I prefer to sand it off. It does clog up sandaper...
If its contact "paper"... the sticky goo glue is a pain in the tail. You'll have to sand it off and use up a TON of cheap 180 to 220 grit paper. OR...

OVERHEAT the covering before stripping, let it cool and the glue hardens up. The covering will be a bit harder to strip off... but the glue will come with it.