Decided to try this now instead of waiting until tonight, result in spoiler:
Spoiler:
Turns out that denial period didn't get me sensitive enough, I couldn't cum from the 500 strokes. I set an hour timer and started stroking, using just two fingers as instructed. I was already hard from anticipation, so no strokes were wasted. It was intense, I was so desperate at times I trembled, but just two fingers proved too little to ever send me over the edge. It took only 12 minutes to hit 500 strokes (500 seemed like a lot, but even at a medium pace I ran out pretty quick). In accordance with your instructions, I won't touch for 24 hours starting now, and will attempt again then. Hopefully an extra day will get me there. :o