"Aha!" Said the sleuth in the deerstalker cap…
I don't use MM acrylics much, but those I have used, dried as fast, if not faster, than Tamiya. I'd consider taking your dilution ratio to 1:1, even lower than Bill's, drop your air pressure slightly, and get a little closer. You have to experiment a little to find what works best for you, what you are comfortable with.
And bear in mind that the conditions around you can have a large effect on the behavior of the paint. High and low humidity are particularly problematic for most acrylics. High or low temperatures also can have a pronounced effect. For example, I have a humidifier in my workroom for winter airbrushing. In the summer, I modify my technique on very hot or very humid days, and avoid air brushing on days when it is both hot and humid.
And don't get discouraged by the apparent complexity of airbrushing. Every time I pick one up, I learn something new.