Here, while you wait for some answers, you can have a few practice runs, may be you can train your penis:
http://www.youtube.com/watch?v=I7JZHCA9rZ4 for the next opportunity.
Brain stimulates penis, penis tells brain it is now in control, brain doesn't care as it gets happy for penis CUMming and tags along the joy ride... plus emptying the reservoir resets a brain cell which controls that function. Then brain thinks it is back in control, but is it really ????