Google search for the "Bayer dip" method...
Lugol's solution is a tried and true method for dipping and post-fragging treatment.
...if you absolutely must do something DIY, but the whole thing makes me nervous.
I currently just give a couple minutes in RO water, and then add them. Ideally you should also quarantine anything afterwards in a smaller setup and watch out for nasties. A 5 or 10 gallon with some water change water from your main system, some basic filtration and/or water movement, and maybe a few pieces of basic live rock (or ideally, some base rock that has been seeded in a running system for a few weeks) and some eggcrate racks is all it really takes.