Drink gallons of milk, eat nothing but yogurt, ice cream, sour cream, drink lots of water. Stay away from coffee, alcohol, illicit drugs. Also try to keep at it longer (sex or masturbation). The...
I have had the same thing happen to me. Cum dries up at tip of shaft, piss is going to exit where least resistance (basically wherever the hell it wants), I have pissed on the wall...
Anything bigger than a baseball bat or 2'x4' may cause discomfort--but there are some girls that can take more than this in. Warn about splinters if attempt to try.