In my younger days, I just washed the airfilter out in petrol, gave it a squeeze and put it straight back in and rode off, never had a problem.
Now, I wash it out in KERO, strain it, wash in warm soapy water, rinse in clean water, strain it and put it out to dry. then Oil with ‘206’ something.
I originally was told to use Turps to clean the airfilter, but found that days later, I’d find oil leaking out of the airbox; the turps would break down the oil over a period and it would settle in the bottom of the airbox.
I rode 10 days through the desert with only one airfilter, with a decent supply of well oiled chux clothes, never had a problem, even cleaned the airfilter in some warm water, then coated it in my spare engine oil…. did the job, but I would have used something else if I had a choice.