With my DBP MK5 GTI I found that using a good pre-wax cleanser before the LSP of your choice was always the best way to achieve brilliant flake-pop. The main one I used then was auto finesse rejuvenate when on waxes and tough prep for sealants - followed by Tough Coat - the flake pop was immense.
Have a look on Polished Bliss - they give ratings to their products and one relates to flake pop - might give you a steer?