Painting Urethane Bumper

I have my front bumper sanded down to the urethane and getting ready to paint it with PPG lacquer. I have been told to use a PPG product PPG # DPX801 which is a non sandable plastic adhesion promoter. I picked up a quart of it today and it is a clear liquid that gets shot just as it comes out of the can ( no thinner) and to apply the top coat right over this product. Has anyone used this procedure before? I was under the assumption that I had to use old fashioned lacquer based primer with a flex additive. Has anyone had experience with the dpx801?