I'm changing my Durance's rear shock oil, and man, it's sludgy in there... Any tips on how to best clean that out before putting the new/good stuff in? e.g. keep filling & draining w the fluid, or tie papertowels to a screwdriver & scrub around like a chimney sweep? I'm open to ideas.

Also, the shock piece/piston I took out to clean, sounds pretty squirty and pumps unsmoothly/inconsistently... any chance that's being caused by sludge having been suck up & in there somehow? ... not sure exactly how that part functions.

Thanks.