I've flushed freewheels with WD-40 to remove the old lubricant and crud, and does a decent job, but not as good as a full immersion. To lube, I've used a thicker/stickier oil, Phil Wood's Tenacious Oil. You could buy freewheel grease injector, if that is your thing: http://www.bikepartsplace.com/discou...injector-tool/