I wonder if you could mix the TiO2 powder into paint reducer for airbrushes, or something like the Flowtrol reducer for house paint from The orange depot. I believe that its possibly a paint base without the color additives. I’m not sure how long it would stay in suspension though. you might need to continuously shake the mixture.
Maybe this method isn’t that great for spray application. Maybe you could get better results mixing your recipe thicker and applying with a small roller.