I've had K&N filters for decades.
They sell a
"recharge" kit with a small bottle of cleaner, a spray can of oil, and instructions.
You'll run out of cleaner way before you run out of oil and/or the sprayer on the little cleaner bottle will break.
Luckily, they also sell the cleaner as a general purpose spray in a
32 oz. trigger spray bottle for less than 10 bucks.