Get Dr. Clark's book, 'Cure for All Diseases'. It's free to download here in the Image Gallery . She explains the proper protocol there. And if I were to buy a zapper today, I'd get one of Parazappers. I bought mine previous to knowing him and his products.
I currently use the SCADA SRG-4 if you want a different reference. It works fine, with the herbal regime recommended by Dr Clark. You need both though. I think parazappers will maybe do it without herbs, since he doesn't use them and has stayed pretty healthy as he wouldn't have if he still had any parasites in him.