My friendly 2 cents: call and ask, figure the tip at the same rate you pay other girls. Go to the pornshop and watch some tranny porn. Then go see your girl. My prediction: you come back and write a review that ends with "... I shot like a horse and Stahu is the motherfucking Man.".
I can never hear that enough.
Then go have a shot, Jack or Johnnie, whichever way your flag flies.
Happy hobbying, pervert!