I'm back to report that the Armor-All works better than I expected. Not only does it make the dried-up, chalky rubber look like new, it works great on the exterior of the lens, too -- whether plastic or painted metal. It's great for lens shades, lens caps, anything rubber, plastic or metal.
Armor-All usually comes in spray bottles, but I would advise AGAINST using the sprayer. It might get in places you don't want it to go -- and you really have to control the amount applied. A little goes a LONG way! I used an old, clean, small, cloth rag and put a TINY amount of Armor-All on it -- just a couple of drops. That's all it takes. Rub it on where you want, and immediately rub it off with a dry cloth.
Works great!!!
I'd show some BEFORE & AFTER shots, but I don't have any BEFORE -- but I'm going to go through my other gear, and I'm sure I'll run into some stuff that can benefit from an Armor-All rejuvenation.