When I used Tamiya paint, I was always too cheap to buy the Tamiya thinner. Always tried some concoction of alcohol, wind sheild washer fluid, water, combination of each, and always ended up with the same problems. Either the paint would dry in the tip of the airbrush, or would dry on its way to the kit, leaving a dusty, sandy finish on the kit.
Once I decided to "Splurge" on the Tamiya thinner, all my problems disappeared, not more drying before it hits the kit, no sandy, pebbly finish. Heck I could even sit my airbrush full of paint down for 5-10 mins, pick it back up and it would still work no problem, no spitting or drying.
Never had as good of success spraying Tamiya paint until I tried it with their thinner.
Of course now, I use mostly Vallejo now, which is a whole other learning curve, but once you nail it, the results are fantastic!