I third that method... Marine-tex is tough stuff. Mechanical removal is the only method I know of that won't damage the rest of the stock.
I have used chemical strippers to remove the stuff from wood before (on boats), but if the stock has anything composite on it, it will at the minimum stain it, and at the worst dissolve it... It will also stain the aluminum anodizing on the chassis... so be careful if you choose to try that method.