Similar to Beating the Meat or Stroking the Salami, this phrasing is a more eloquent way of saying you are going to self gratify.
After leaving the Strip Club: “I think I will be Getting Randy on my Johnson as soon as I get to the car”
Holy smokes Chris just got an R.J. (A Randy Johnson) from that absolute dud. She looks like she’d throw gas with that kind of velocity!