I am surprised to read some post here that are still using the old school method of "Petrol - Turps - Kero'
Each to their own method, but I was taught that this is WAY TO HARSH on the filters and will do damage to the foam. If it works for you and you like it ........?
I buy cans of cheap and nasty (NON mineral based) spray on de greaser. I spray the filter foam and massage in well. Then it's just a matter of rinsing on warm water, then washing in CT18 truck wash, again rinse in warm water. Then I use my air hose and blow all the water out (Hate waiting for it to dry in the sun). Once it's nice and dry I then immerse the whole filter in liquid filter oil and then squeeze out ALL the excess. It then ready to use.
Someone here posted that cleaning filters sucks ? It's part of living with your bike. Any time with my bike (riding or maintenance) is easy time. Sitting in the shed, music on, beer in hand, son by my side learning, that's what its all about !