back painting

the act of ejaculating on a back upon pulling out; cumming on the the back region

yesterday me and sarah got down and dirty, and then i gave her a back painting

Back paint

Busting a monstrous load of jizz on ones back!

I back painted Molly last night after she gave me road head from the bar!

Back in the painting

To be "Back in the painting" means falling back in your old habits. If you we're a portrait this act would be portayed.
Also used for more short sighted terms like when there is a bowl of candy on the table and you exclaim, i'll have no more and then two minutes later you are – indeed – back in the painting

I'll have no more candy now. (moments later the person eats more)
I'm/she/he is now "back in the painting"