timoteo - just take an old soldering iron (you can use a new one but it will soon be old :-) and score it down where you would normally cut it. don't move too quickly but slow enough to seal the covering on the wood. you can test on some scrap first so that you know about how fast you have to move. after that you can remove it by cutting a flap with a blade (careful not to cut he wood) and then from that pull the rest of the covering off. if it rips off incompletely, you can just use the edge of a blade to pull off another flap.

i use the soldering iron for things like burning aileron lead holes in dual aileron wings and other places where the burn mark isn't so evident.

since doing this i never use my razor unless i have to. i always have a fear of cutting too deep and compromising the structure.