For the front rings, I go to a hardware store and find a piece of pvc pipe fitting in the plumbing section, or improvise a similar correct-diameter hollow tube. Then I tear thin strips of duct tape to make a cushion on the edge of the pipe fitting. This cushion gives friction so I can push down on that lens ring to try to get a "grab" so I can start turning. Sometimes it works, sometimes it doesn't. Usually does eventually though. As for the super-tiny set screws, if you use a 50m lens turned-around-backwards, you will see that many of them actually have a very wide slot, and the cheapo screwdrivers may NOT be wide enough, and the slot therefore gets torn up beyond hope if you're not careful. I'm convinced if you send a lens off to Hassselblad or somesuch firm, they just throw away the screws and use new ones when they put your item back together. We don't have that luxury.