I know popping an cap before loading an sidelock for an range session or an hunt is the norm. I pop two or three before I load. but I worked up an theory about using an air compressor to blow the oil out.

first: run an alcohol patch down the barrel to remove the oil.
second: take an qtip soaked in alcohol and clean out the booster (powder drum) (if possible)
third: place an patch at the end of the range rod, either from the nipple or the clean out, with proper fitting. blow the air thru the gun.

I won't be able to test this for an few more weeks. just wanted yalls thoughts on this.