I stuffed rags into either side of my axle when I did all the grinding/drilling. Still though, I had shavings and such down into the axle tubes. i had the axle housing off the truck with everything out of it so lifting it on end and blowing it out wasn't a problem at all. I used a bit of brake clean down there as well. It sounds like maybe you still have your axle on the rig? If so it would probably be a pain to remove the stuff. See if you can borrow an air compressor with a long flexible nozzle.
