Hikarus, Gunze is my acrylic of choice, and I use them for practically all my painting. Like you I have found these to be about the best acrylics, both in terms of the paint quality itself, and the range of colours available.
As for thinning, just use Tamiya acrylic thinner at a 50/50 ratio. You can use water, but it doesn't have the retarder that the Tamiya thinner contains, and thus you are more likely to encounter tip dry while spraying.
Karl