I've decided to transition to Ferrex from Iron X simply because Iron X comes from South Korea, making it difficult to get sometimes. Luckily Ferrex works pretty much the same and I can get it anytime.
This is the product we use for Step 2 of the Decon process (after strip washing). I've used six or seven different versions of this type of product to chemically decontaminate the paint. This breaks down iron that embeds itself in/on the surface of the clear coat. I'd also like to note that they all smell bad and this one is no exception, so prepare yourself for the stench. There seems to be no way around that.
Contrary to conventional wisdom, I find that iron is most apparent on new cars right off the showroom floor. They tend to pick it up in transit from ports or railways. But I use this every time I decon the car just in case.
You could watch the video above if you'd like, but I use this like so:
Immediately after washing with Decon Soap, rinse the car thoroughly. I use deionized water.
I spray, liberally, all painted surfaces, glass, wheels (avoid brake rotors), lights with Optimum Ferrex. I don't want to purposely hit plastic trim and rubber, but it's usually okay if you get some overspray on it.
Let sit for 5 minutes. Don't let dry. I don't know what will happen, but I don't want to find out.
Rinse thoroughly to prepare for next step in the Decon process, Autoscrub or Clay. I always rinse with de-ionzed water.