Slappin’ something on is something I hear frequently in my neck of the woods.
“I’m gonna slap a little paint on the walls.”
“Let me slap on a little makeup before we go to town.”
We don’t actually mean physically slap, like you’d do to someone’s face if they get on your nerves. We’re just saying we’re gonna put something on. Sometimes, slapping conveys that the task is done without a great deal of precision. For instance, the paint probably won’t look like a professional did it. On the other hand, the makeup might have you resembling a professional you didn’t intend to.
The next time you put something on, let your inner Southerner loose and slap it on.