No experience with slides to really speak of.
First stop is canned air. If this doesn't work, I use cotton gloves to very lightly polish a small water mark - this may get me shot here though! Failing that, Tetenal film cleaner - which isn't as effective as it ought to be - with the cotton gloves - I'm told a soft camel hair brush is good with it but brissles on negs sounds silly to me - however soft. Pec 12 is meant to be the best stuff but I keep forgetting to pick some up when I order. Finally, for strips, rewash in distilled water and photo-flo (wetting agent) can work. It all depends on the marking.
