what paint/epoxy you guys use

If you want to add color, you will need to use an epoxy, not paint - not even "floor paint" as it will not hold up well.

What I used is called "Cure & Harden" or something like that. It is not a film forming product, it soaks down into your concrete and literally hardens the surface by many times over. It is a clear liquid, comes in a 5 gallon bucket, easy to apply. I did my showroom floor with it. We literally drag wood stoves across it with no damage at all. In the warehouse I did not use it, when we drag or slide a stove, the legs literally plow across the top of the concrete, creating a dusty scrape.

I think the product also blocks stains, but not sure, worth checking into. I will definitely be using it on every slab I do in the future.