My advice is to consider the fact that you have 99.5% purity acetone a stupendous, miraculous event and to proceed ahead with the extraction. I don't know what else to say. Your acetone is perfectly fine, amazing even. There is nothing to dry... the .5% of impurities is most likely metals and salts, not water. Even if that .5% was 100% water, who cares you're looking at one half of a percent. Since in all probability it isn't 100% water, you couldn't remove the .01% water or whatever it MIGHT be in there even if you wanted to.

If you had acetone from the hardware store, yes by all means add a desiccant and dry it out.