Well.....
steel wool is a bad idea because of all the VERY rustable bits it leaves behind.....even using compressed air, they seem to linger wherever they can. No on the WD-40. You could rig a 'swab' to coat the inside. I'm thinking auto paint clear....or maybe the sealer they use on tile/grout? They even have plastic sealers which might work....I would think their lubricity perfect for dirt & air. 
I could use an extra wand for my as-of-yet unrestored Anniversary model PN2. The wand at the top where you insert your hose tool, has a broken friction ring and non-existent Teflon ring. Those are riveted in there and I haven't taken that puppy on yet. Probably easier just to find another wand.
Kevin