Now, yes I know you should always check and spray a bit of paper or something. Talk about a noob mistake. All I did was clear the nozzle out into the cold night air. then give the tank a good short blast.
F$^%&, F$^%&, F$^%&
So I rush inside, grab the turps and a rag, and start rubbing. The thing that saved me is the two layers of hardened gloss varnish. After several minutes of cursing (thankfully the wife wasn't home) I've ended up with whats below. The Red star is the side that didn't get a coating of white primer.
An Epic save in my books.
Time to stop painting and go get a huge glass of scotch.
The tank needs a good wipe to clear off all the fluff from the rag i used to clean it, and then fix up the tracks and wheels. That can be for another day.