steveh op 9 January 2016 · 19:10
You should only use base cleaner when you need to repair a patch of the base, as Ptex will not stick if there is wax present. In this case use it on the repair area to get all wax out before applying Ptex.
However, you might want to clean out your bases as new bases do contain a lot of dust, but you do this with hot scrapping, not base cleaner. It is much more efficient at cleaning and it's cheaper too. Just take some wax (the cheapest you can find) and give your skis a good waxing. Leave them a minute or two until they are cool enough to handle then scrape off the wax while it's still warm. This will remove dust and dirt from the base; you should see it in the wax as you scrape it off. Depending on how fanatical you are you can keep doing this until the wax comes off clean, but personally I've never done it more then twice.
Once cleaned you wax again as normal, let the skis cool then remove excess wax and brush the bases (or not, it doesn't make a big difference in the long run unless you are a racer).