The most painful e-stim on the nipples I have ever had was using a Olympian piezoelectric sparking furnace lighter. My husband punished me that way when I was mummified in 2018 a week before Thanksgiving for having an “unapproved” orgasm given to me by friend Beth in the middle of the night. You can buy them at Wal-Mart, Amazon and Home Depot.
About a month ago I mentioned in a bondage thread that I was going to have my first colonoscopy and that my husband wanted to mummify me. We checked our schedules and it works out that my first colonoscopy will be followed the next day with my mummification.