You know what. Whatever way you put it in, it wont work initially. Just shove your tool in any way it will fit, and wiggle it about. I simply spin the tool around, making contact with the S1, till the percentages rise, then try and hold this position.
I think you want to use the tool "I" way, but honestly, you may find a spot that works where your tool is "-" way, so its sort of luck.
If you use foil you can find the contact right away. Unless the toothpick is also insulated wiggling it around would be a bad idea.