Scraping it off with your finger nails of a flexible plastic would not be a problem. The RTV sealer should come off very easily with no use of force. Now, uf you roughened up the surface, that is a different strory.

By the way, to those who are considering RTV sealing your engines, dont roughen up any of the surfaces.

If you did roughen up the surfaces before putting on RTV, just scrape it off as best you can with a flexible plastic and put on a new RTV layer over the old.