Next time I do this I'll hire a pro... surface prep is the hardest part, and they have the better chemicals and equipment to do it right, including grinding the concrete first if needed. They also have a warranty.
I used some 2-part epoxy at my first house on new (and fully cured concrete) and followed the directions to the letter. It still failed within a couple years with massive flaking. I ended up putting down vinyl rolls to cover the floors and they worked great.
My current house had nice paint on the concrete front porch and steps, and in the unfinished portion of the basement on the floors and walls. Previous owners DIY as far as I can tell, and probably right before they put it on the market. 2 years later it is failing as well.