The quirt she's using is quite savage as there appears to be metal attached to the ends which would intensify the pain. Then again, although the slave makes quite a lot of noise, he is able to take severe discipline and always comes back for more.
I Love having My Bare Ass Teased with a Lit Cigarette while I'm getting a Hand Job in the Diaper position. I shoot Ropes of Cum all over Myself in know time at all. Lol.
Wife did that to me several; times but burned shaft right under head. She liked to keep it there until it was going to blister. Better than this was an old HO train controller run one wire inside urethra move other on up and down outside while varying the voltage hurt to pee for a couple days,