I just cleaned and re-lubed mine a few weeks ago. You have to uscrew the fron lens assembly before you remove the aperture ring. Once you have the aperture ring off (2 tiny screws), you can pull the ring off. Then clean both the ring and the mating surface (on the lens body) with lighter fluid. Apply a very thin film of synthetic grease (I used white lithium bicycle bearing grease). Reassemble.
Previous to doing this, my lens would freeze up immediately in cold weather. Now, I can have it out in 20 degrees below freezing, and it feels smooth as silk.
There was a very good explanation on this forum, with pictures, of how exactly to disassmeble the lens. I'll see if I can find it. Also, it helps to have a lens wrench that will allow an even grip around the entire diameter of the front assembly. That way you have no chance of ruining the finish.
Okay, here's Victor's post:
Here is the spanner that works great to remove the front lens assembly. The larger of the two is for the Summitar: