Absolutely! I understand it's best to thin it (with the manufacturers thinner, for best results) to about the consistency of milk. Ratios? I think it all boils down to consistency. And I believe the acryl paints should be a different consistency than milk; check the forums.
Obviously, you'd need to use water for the acryl paints and thinner for the enamel ones.
Also, I'd suggest sifting through the forums before you post a question that has undoubtedly been very well documented many, many times.
Happy modelling!