If you have not removed all the covering, then try removing the balance with some heat.If the covering has seperated from the adhesive and color pigment this is what i do.Get a 1/4x1/4 peice of balsa and sharpen the end so you have an edge, you don't want your scraper harder than the balsa your scraping.Now with your heat gun heat up the residue till it softens and scrape off as much as you can.That will get most of it off, the balance that is left use some lacquer thinner and a cloth and rub it off.You will still have some color bleed left on your balsa frame work, but it will be smooth enough to recover.Hope this helps Chris.