I get hard the moment my spanker takes down my underwear. Once OTK, and we are lap to lap, there is a gradual build up. Pain of the spanking, leather straps and paddles will ward off the hard-on, but it usually it comes. As the pressure of my glads against his leg, or the pillows propping my ass in place, take over, the orgasm can happen. I find this will happen when the spanker tells me to present my ass ( prop it up) for the lash of the strap or paddle, and the swat forces my cheeks to clench, and pelvis to press down. Continued repetition like this, swat by swat has made me cum while being spanked. And yes, a continued spanking afterwards is even more painful, and sometimes that punishment is fully deserved.