This Optimum Clay Bar, the AutoScrub Sponge, and 6" Pad are what I use for Step 3 of the Decon process. You can use soap and water, detail spray, or a dedicated lube like Glide for this "mechanical" part of removing contaminants that are embedded in the surface of the clear coat.
Not all clay is the same. I find many companies over complicate it. This one is very simple. That's the reason I like it. I use AutoScrub most of time but find it necessary to have a clay bar in the cabinet for dirty areas or tighter spaces like a front bumper or head light. It's also much better for overspray or heavier contaminants.
You could watch the video above if you'd like, but I use this like so. This is the third step of the decon process.
Immediately after "chemically" decontaminating the car with CarPro Iron X, rinse the car thoroughly. I use deionized water.
I spray 7:1 diluted Glide liberally, soaking the panels you want to decontaminate. I usually start on the glass then work my way from top to bottom.
Use this clay, AutoScrub Fine Grade Sponge, or 6" Pad on the surface of the paint to remove the stuff you don't want there. Glide is the lubricant we need to reduce marring and scratching during this step.
It really doesn't matter if Glide dries on the paint because you are going to be polishing, but I like to rinse off after I've done a few panels. It will dry a bit streaky if you let it.
Rinse thoroughly and dry the car. I always rinse with deionzed water.