I think it is just a matter of playing with the thinning ratios. I personally don't mix mine with water, and use the thinner (thinner/reducer...same thing).

Give the Model Air a try before you give up completely, and it is just a straight dispense and shoot, just not as many colors to choose from.

I have been using these for airbrushing for about 5-6 yrs, the first couple there was some frustration, but after awhile I got the hang of thinning them. I never said it was easy, but in the end the results speak for themselves.