I like the maxima air filter oil and cleaner. Typically throw it in a ziploc bag with the cleaner and squish it around for 10 minutes or so. Rinse, Rinse, Rinse.
I let it dry and then give it solid coating of maxima air filter oil. It's blue and just the right consistency. Doesn't drip or run.
Back into a clean ziploc and on the shelf for when it's needed.
-BIG DAN
I use the No-Toil/Cleaner kit. Fill the sink with warm water, add the beads, dissolve them and then fondle the filter under the water until it's all clean. Rinse from inside to out. Let it dry. Then spray a light coat of the oil and again, lovingly fondle the filter until it is thoroughly and evenly oiled, then let the excess oil dry out.
First Paint Thinner aka Mineral Spirits. Then Dawn dish soap and water.
I've got a bit of a problem though. CARB has banned the paint thinner and mineral spirits that I've always used. I'll have to buy a stash before it's outlawed on Dec 31.