Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison
Ideally use discharge for the white, and we're finding more and more that p/f/p of the adhesive works betterfor a lot of foil colors, especially with fine detail and/or large coverage.With just plastisol for the white I don't see a way around the problems you've described, your best betbeing just pressing the foil area and doing what you can to mitigate pressure marks. IE use a spacerto raise the area you want pressed above the area you don't.
As has been noted: PFP the adhesive. Superior results.Use either a textured teflon sheet or craft paper to keep the plastisol from getting shiny under the heat press.
Does the foil not adhere to the plastisol ink when the foil is applied? I was told that is does and should use waterbase inks where you did not want foil to adhere. That could be wrong info I was told. I am just asking as clarification, not providing information.
Side note, virus foil adhesive is the best stuff on earth.