Remember that electrical current needs to travel from point A to point B, and that electricity, like most things, follows the path of least resistance.
if you have a pad or loop on the shaft, then the current needs to travel to (or through) the base of the penis. placing pads on your back makes a LONG pathway and you'll notice little effect.
if using loops, since their surface area is smaller, that's where you'll feel the effect.
the larger the pad, the larger the surface area, and the lower the "skin effect" or tingle/buzz you will feel at the pad site.
I've had decent results from applying one pad above, right where shaft meets tummy, paired with a pad on the bottom of shaft (on the south side, if you are pointing out)
If I'm using both circuits, then I'll add a pad below (in the taint area, just below the sack) paired with a pad on the top side of the shaft (north side, if pointing out)
I typically will e-stim while wearing a nappy, and since moisture will complete circuits rather quickly, I'll use a stuffer or baby diaper against me as an insulator/to help the taint&top pad stay in place, with the head and shaft (if not the balls as well, if they aren't tucked up and in) passing through a hole in the stuffer.
when completely dry, a setting of 2-3 on a scale of 25 is PLENTY.. as things get wetter over time, and nerves deaden up or become acclimatized, the setting can gradually increase all the way to 25.
I'm using a basic "accu-relief" tens unit from my local rite-aid and it works fairly well. good enough for an introduction to see if you like E-stim and reasonably low cost ($40?)
I plan on upgrading at some point as the options are somewhat limited. I've also used a "nexwave" by zynex medical and the IFC mode with 4 pads is way more.... stimulating...
Always remember to do research, and educate yourself before playing. turn off, and then disconnect the tens unit before repositioning or touching placed pads.
ALWAYS below the belt, and avoid any far reaching cross-body placement due to the risk of current travelling through the heart or nervous system in a non-desirable way. start with the lowest setting, and with pads closest to the area(s) you want to affect. slowly try other positions slightly farther away, or higher settings. a small variation of 1/4" in placement can have a huge impact on sensation and effectiveness!