How about if sub #2 has the fuck machine instead of the stool, the speed of which increases in line with the time he takes to get PuppyKaiden off. 
The sound sensitive estim as mentioned by jimmycontour above is a great idea too. Perhaps if Sir had the control of an estim connected to a butt plug up sub #2's ass and increased the voltage until it made sub #2 howl and the sound sensitive estim was round the pup's balls, therefore putting him off an orgasm, it would make sub #2 try and keep quiet and focussed on the pup's dick. The longer it takes the more he gets shocked and the more he howls the less likely PuppyKaiden is to get to cum.