This is the method I have been using for the last two years:
http://www.castironcollector.com/electrolysis.php
I've cleaned maybe 3-4 dozen pieces of cast iron cookware so far, a bunch of tools as large as a post vise and lots of odds and ends. Works beautifully. Get to scrubbing and rustproofing as soon as it's out of the tank. I season the cookware with canola oil using the method on the same website.
I started out cleaning cast iron cookware with lye (spray-on oven cleaner) , a scotchbrite pad and elbow grease. It can certainly be done that way and if you have a limited number of items to clean I recommend it. (Unless you are cleaning a cornstick pan, which is the path to madness.) But the electrolysis tank is way easier once you get it set up. I still presoak every pan that looks like more than pure carbon (i.e. anything possibly greasy) in a lye tank -- a 5 gallon bucket for anything the size of a #8 skillet or smaller, clean the greasy stuff off, and then it goes into the electrolysis tank.
As far as stainless and hexavalent chromium goes, I've seen arguments for both sides -- that it might be a byproduct of the reaction and it might not. I had so much trouble keeping carbon steel donor anodes clean enough to be effective that I switched to stainless, which is much easier. But, choose your potential poison. Find a cheap source of wide, flat graphite and you may get the best of both worlds. Clean anodes with lots of surface area make for efficient cleaning.
With us, the attractive and collectible skillets decorate one kitchen wall, the interesting bakeware goes in the dining room, and anything else that doesn't get used much is given to friends and family who have yet to discover cooking with cast iron. My wife cooks and bakes with vintage cast iron 90% of the time.