Leo;
I live in Arizona and we have a pretty dry climate all the time. I have tried many things and my current "formula" of choice is 1 drop of retarder (I use Golden's), 2 drops of Flo-Aid by Liquitex, and then bring in the paint. I then thin as I think I need to based on the pressure and the color. I still keep a swab nearby and clean the tip often.
I spray Tamiya, Vallejo, and Model Master and it works on all three brands. I would assume the Tamiya would as well.
John