From the song Hey Ya by Outkast, the phrase "shake it like a polaroid" means to shake like the act of masturbating. One developes a polaroid by flicking their wrist in a back and forth motion.
Bradford went to shake it like a polaroid in the bathroom, but found his brother already developing his own polaroids.
When a man masturbates and then ejaculates into his hand then throws the semen over his shoulder for good luck, much like how people throw salt over their shoulder for good luck (hence: Chinese Salt Shaker)
Dylan-"Dude, i just did a Chinese Salt Shaker so we're definitely going to win our game today!"
Nick-"DUDE, THATS DISGUSTING! You didn't need to tell me that."
A retaliatory action where a man jerks off in a girls purse, closes the purse, and then proceeds to shake the purse so all the contents inside have an even coating of jizz on them.
Dave: Did you hear what Mike did the other night to that chick he hooked up with?
Mike: No man, what did he do?
Dave: Apparently, the girl stopped having sex with him once her boyfriend called and she decided to leave. Instead of being blue balled Mike jerked off in her purse, zipped it up, and shook it up in retaliation while she was in the bathroom cleaning up.
Mike: Holy shit, he shake and baked her real good. I bet she was pissed.
Gary: Hey do you want some shake n bake?
Bill: Sure, i could use some food...Gary where did you get that child?
Gary: I give birth very quickly *Shakes baby*
Bill: *unzips skin*
Gary: Really? Infront of a child? *Throws baby in oven*
(30 minutes later)
Gary: Ok Bill, dinner is ready