I’ve been weightlifting consistently for about a year now, and starting to get some really good results. One of my silly goals is to do the magical pec dance, where I can operate each one individually for a hypnotic booby-jiggling show. Does that come with increased chest strength, or is it only reserved to a special few, a la ear wiggling?
Anyone can do it, I think. It’s a matter of size. Any puny kid could do it but you wouldn’t be able to see it. It’s simply alternating between pulling the right shoulder forward, then the left. When people do that, you often see them clasping their hands together. That’s so their arms don’t move when they contract the muscle. Try pulling your elbow down and to the front. If you’re big enough, you’ll dance.
Alternatively contract and relax the muscles in your chest, according to my husband.
You call your pectoral muscles ‘boobies’? How seriously do you say you weightlift? 
I could benchpress you into space.
Like Po from Kung-Fu Panda? Skidoosh!
(OK I’ll stop being silly now)
Get your muscles to think you are doing pushups. Think of doing one, and the muscles it would require. Then imagine you are doing a push up with just one arm, and then the other. Your boobs should be flopping away in no time.
Not that I’ve practised a lot, but sometimes I get my pecs to dance for a couple secs, almost by accident. It’s a combination of relaxing some muscles while activating others nearby. It seems to come easier after bench pressing. But as soon as I try to do it, I fail. Pulling my shoulders forward does nothing.