well a few things, first, like the two guys above, gummy stone is the way to go in terms of getting rust off. second, yea you can drop ptex on the bases anywhere. you can even get some on the edges, no biggie. That being said, you then need to scrape it off which you can do two ways. One with a razor by hand or two with a wintersteiger. I would say just take the ski to your local shop and have them tune it. the 50,000 dollar machine will most likely do a better job than you in your garage. hahaha, not saying you cant hand tune your ski, but someone who gets paid to do it, will do a better job. hope this helps!