hey squeeforever, i have never used nitro fuel to wash the filters since the methanol temporarily makes the foam swell right up. HPI recommends it, not me...i recommend mineral turpentine.
i use k&n filters all the time. If you check out their website, they have a r/c specific filter, but they are all connstructed the same, most on e-bay are actually oil breathers. In fine dust use a pre-filter, other than that keep it clean and well oiled, i've had lots of luck with them and actually had my engine temps come down because of the easier breathing