Hi benchracer1, new guy to the forum here, not new to concrete coatings though!
Glad to see you are going with the epoxy/urethane system over polyaspartic system. I think it will be much easier to apply and last longer. I am not familiar with the manufacturer you are using but would like to offer a few pointers if you are not underway yet!
Grinding that floor is a surefire way to guarantee success in a floor coating, prep is key as you know. If you still cannot get rid of those oil spots a Muriatic (Hydrochloric) acid bath + pressure wash may be necessary. Be sure to sprinkle some mineral water over any areas that you're unsure of, if it absorbs GREAT! If it does not, further preparation is required.
I, personally, am a fan of randomly broadcasting my slip resistance sand into my first epoxy coat while it is still wet. Then rolling back over that with my second epoxy coat after it cures and finishing off with a clear or opaque CRU!
If you do decide to add the 2-4 oz per gallon of sand to your final clear coat there is nothing wrong with that either. Be sure to periodically agitate the material if applied out of a bucket so the sand remains suspended. A pan or tray is the recommended method though. Ribboning the liquids and then spreading the material with a flat squeegee is not recommended since the beads may lay out unevenly, resulting in a patchy appearance.