Do a thorough cleaning and let the filter completely dry before spraying on the oil. This will likely take a few hours (the cleaning takes 10 minutes, the drying takes forever). Remember to let the water running over the filter flow from the inside out, so you do not drive any dirt further into the cotton element.
I usually make two quick passes over the cotton element with the filter oil spray, starting always from the same end (you can pick, top or bottom). I spray from the outside of the filter, never the inside. Then I let the filter sit for a bit to let the oil flow from top to bottom, and then flip it over and let it flow from bottom to top. In the end, its pretty even.
You will also need to spray the middle of the cone, from the outside again. You do not want too much oil, so let it sit for a bit for the excess oil to drain off. Just enough to get it reddish-pink is what you want.
