Do you add a little grit so the floor is not too slippery when wet?You can rent a carbide scraper that mounts to a standard floor buffer. Any good rental place should have them. It will scrape off any old floor coating, and any little bumps. It will not level the floor.
https://www.sunbeltrentals.com/equip...-tooth-driver/
Applying epoxy isn't much different from any other paint job. The better the prep, the better the results. My garage had been used for auto repair for a few years, by me, before I decided to lay down some epoxy. All the greasy spots got soaked several times with mineral spirits, (paint thinner), then cleaned up with kitty litter, then a few washes with a good degreaser, then a couple etchings with muriatic acid, (this stuff is nasty so be careful and have the good air circulation. Then follow that up with a couple more degreasings to neutralize the acid. Let it dry good and apply like you would with any house paint. Mask the edges and edge in with a small brush and then use a roller on the main part of the floor. You may need a second coat. Some guys use and old pair of gold spikes to walk on the first coat and not leave foot prints. Generally you need to apply the second coat before the first sets up , right after it stops being tacky. If you wait too long you might need to wait a couple weeks, sand it lightly, wash, and apply the second coat.