Actually if you had to go through with in real life I recommend for practicality's sake that you use something like joke powder.

This is something I tried a while back. I cuffed and gagged an old girlfriend once and sprinkled a reasonably large amount of the itching powder on the flat of her belly and then tickled her using a feather boa. It took all of 30 seconds before she started writhing and moaning and after about 15 min of that I let her up by which time the entire area that the feathers had touched had turned a bright red. She later described it to me and I quote "It felt like I was being bitten by hundreds of mosquitoes. I was terrified that you would rub the feathers with itching powder on a sensitive spot like nipples or my cunt."

It was one of the hottest bit of torture we ever did.