Popular 3 coat epoxy floor system for 400-450 sqft includes a primer:
The most popular primers are AD15 and AD144.  AD15 can be used for all priming needs even indoors such as basements.  AD144 is used when a fast drying primer is needed and where odor is not an issue.  AD144 not available for sale in the following states, CA, CT, DE, IL, IN, MD, ME, NH, NJ, NY, OH, PA, RI, VA.

An exellent 2 coat single color thin mil epoxy system is a primer and pigmented urethane such as AD322.  AD322 not available for sale in CA.  CA residents use AD358 with color pak.  AD15 and AD358 is a high traffic commercial grade single color flooring system with non-skid.

For floors prepared by shot blasing and a high build is required use AD707LVP as a primer. 

AD820 is typically used on floors where large oil stains can't be removed and for oil contaminated wood block floors.  Wood block floors should be shot blasted before AD820 is used.  For oil contaminated concrete floors degrease with a quality degreaser then acid etch.  If water still beads up use AD820, if not then AD15 or AD144 will work fine.  AD820 comes in black only.