Using Tamiya and the Model Master water based what % of paint to thinner do you guys use?

I usually thin the tamiya acrylic about 60/40 paint to X20 (their thinner) or a mixture of 50/50 isopropyl alcohol and water with a touch of retarder and wee drop of detergent to combat tip dry and improve flow. I normally shoot at 18-20 PSI for broad coverage, and drop to 10-15 PSI for more detailed work. I also thin the paint to closer to 50/50 paint/thinner when working at the lower pressures. The Model Master (which I very rarely use, prefering the tamiya) I normally knock down to 50/50 with distilled water and a little detergent, again to improve flow.