House painter's lingo for smoking marijuana before or after actually painting. Much better before yet not so bad after.
Putting on a painter's cap = Getting high!
Painter: Hey Dude, let's put on a painter's cap before we tackle that living room.
Painter 2: You got any?
Painter: You know it dude. Straight fire!
Painter 2: Awesome! Let's do it quick before the boss show's up!
Painter: No worries man! Who do you think I got it from?
Painter 2: Nice!