I cleaned my K&N drop-in air filter last night and set it on a wire rack in a dry room; 12 hours later, and it still seems damp (or maybe that's just the residual oil?). How long does it need to dry before oiling?
well if you let all of the water dry out first its residual oil and it wont hurt to put it back on I have put them back on way before the time frame you mentioned
You have to make sure it's utterly and completely dry water-wise before you spray the grease on. That stuff should dry in minutes.
... and be careful not to over-oil it or you'll be running rich.