Colt can be a pain to deal with. I would cut it in to roughly 3" long pieces. For harvesting I would take 2 or 3 pieces at a time. As far as adding iodine I do not know. I would preform a water change a couple of hours after doing the cutting. If you can take it out of the tank to do the cutting that would be better, although not always possible.
The larger the pieces the faster they will attach and heal.
I just use sissors and immediately take the cutting out of the tank and into a small container to attach it and let it slime. Change the water in the container a few times using tank water and it will stop sliming and can be put back into the tank.