>- Apparently a dry hand can have an impedance (resistance to electricity) of up to ...
I am not sure if the figure that you quoted is correct but it can be high. The problem with high skin resistance is that very little current gets to the places where it is most needed. Ideally, you want the lowest skin resistance possible. High skin resistance can cause burning at the skin.
>- haven't been particularly impressed with Parazapper
Which model and why? They are designed with safety and reliability in mind.
One reason that I ask is because there are sites flasely claiming to be ParaZapper. Also, there is a tremendous difference between the cheapest model of ParaZapper and the best.