I'm ready to begin my experimentation with silicone cock rings. From what I've read you can wear these around your cock and balls, or just around your cock. So I went shopping at Hustler Hollywood, and the expert there told me these always go around your cock and balls. He says just wearing one around your cock doesn't really do anything. So he's an expert to me only because he's worn them a lot and I've never worn one. What do you guys say? Cock only or cock and balls?

I do both.  Sometimes, one at a time, or two at the same time. One on my cock and one around cock and balls.  Works great for me.  
The one just on my cock enhances my hard on.  The one on my cock and balls, enhances sensation for me.  

Once for me. A Vegas escort of some renown slipped it on me and we went to town. I didn't ask for it and she didn't pre clear with me.  

Several years ago, I went to a leather S&M clothing boutique to get an outfit for a photo shoot. On the counter were round silver rings and I wanted to try one on, but I couldn't figure how to get it on my wrist, because the 'bracelet' was too small. I asked the clerk about my dilemma and she laughed sooo hard, she cried. Amazing, in all my years of sexcapades, I'd never heard of a "cock ring." To this day, I've never had anyone wear a "cock ring" with me. Perhaps that will change in 2017!

...I think your looks and rated performance would make a cock ring superfluous

I am not a frequent user, but when I do, I find that the rings that have two parts: one to encircle and hold the testicles at the base and the other for the penis really make for great and prolonged feelings

I've also seen them used to partially offset ED issues, with causes ranging from Parkinson's to circulatory disease to coke dick.

Doing my best to not take the fun out of it....but a cock ring around just the cock logistically acts like a tourniquet to keep the blood flow there and keep you erect. around the cock and balls....more blood, more arousal more sensitivity. With all the medications we deal with today.... blood pressure, blood thinners etc...you don't need ED to have difficulty with maintaining an erection. Now for the fun part....cock rings can intensify orgasm and make you more sensitive. You can head to your local pharmacy now and find a variety of cock rings...my personal favorite are the ones that have the small vibrator at the top and bottom...delightfully vibrating for both parties! Play around and make them a fun thing. I know it helps way more when you don't need the assistance but call up your ATF Provider and experiment. Make it fun!