Why not just use an Ohm-meter.
But Regardless of what you use, you need a GOOD Contact Points.
CONTACT RESISTANCE is Your Greatest Problem.
If for example I hold my Ohm Meter Probes, one in each hand with DRY Skin, I get a reading in the High Meg-Ohms.
If I wet my Probe to get Good Contact, I get a Reading in the LOWER, Thousand of Ohms.
If the Skin has Sweat on it, It will have a High Salt Content, Resulting in a Very Low Surface Resistance.
The Resistance Measurement will be Mostly from that Moist Salt, Not the Actual Skin.