I haven't heard anyone say this method yet so here goes:
I use clear plastic Scotch brand tape (not "Scotch tape") this stuff must be 1-2 mils and is stronger and tougher than cellophane or magic tape.
First I clean the inside surfaces of the clamping band (especially on front derailleur bands, shift levers straps and water bottle bands..) with alcohol..
Then apply the tape to the inside of the surfaces. I trim the overlapping excess with a sharp Exacto knife.
Care must be taken while installing as the tape thickness reduces the effective diameter of the clamp and makes them a tight fit. If you are not careful you can actually accidentally pull the hinge apart on a Campag front derailleur band!
But once in place, the fix is invisible and can last a while as a gentle cushion to protect the paint. Eventually solvents and heat will break down the glues on the tape and it will have to be redone....
Dale Brown
Greensboro, NC