Can you get a sample of the soy based paint stripper beani doo or something like that and try it. If you used that type of product and are able to strip it all back then you can acid etch the slab afterwards with muriatic acid and water. For DIY that is quite good.
If you use a diamond grinder it can be a) very fast and easy, b) moderate to slow, or c) painfully slow and extremely difficult depending mostly on the hardness of the concrete, but also on the type of paint used. Acrylics will melt and if the concrete is hard too it will be very difficult to remove by diamond grinding, if the concrete is soft it will be easy.
Two other problems you can have with diamond grinding (which I think is the best method if you are a pro and have all the equipment and experience) is leaving ring marks and opening air holes that can cause bubbles.
Another way that is less problematic than diamond grinding yet it uses diamonds is Diamabrush which you will need to source from a supplier. I think Legacy Industrial said in another post that they supplied them.
