A Fluidized Polymer Suspension (FPS) thickener comprising a hydroxyethylcellulose and/or alkyl or arylalkyl hydrophobically modified hydroxyethylcellulose added continuously to an aqueous dispersion increases productivity for manufacture of aqueous coating compositions. The FPS can be stored and metered without delays associated with dry powders. A latex paint is continuously produced by simultaneously or sequentially mixing latex binder, dispersed pigment and FPS thickener along with other ingredients.