I use both Flotrol and washer fluid . The Flotrol alone provides greater flow out of the paint once its on the surface but doesn't do much for thinning the viscosity to get the paint through the gun in my opinion thus the need for the washer fluid also . Don't over apply the paint . Once sprayed it looks very orange peelish and you might want to spray more on to get that glassy wet look , DONT .... It doesn't lay down smooth like automotive paint on initial application. The Flotrol will level it out as it dries . Apply only the coverage you need and leave it alone .
What ratios are you using with the flotrol and windshield fluid?