Remove grill from car, sand with a 420 grit sandpaper untill everything you want prepped is not shiny. Wife off the sanded part with wax and grease remover. Get one of the three cans of plasti dip you purchased from either Lowes or Home Depot (in the spray paint isle, in the speciality paint section) and spray on light even coats.
It will take seven or eight to do it right.
Plasti dip will sometimes clog up and spray in clumps out or the nozzle, don't worry. You can sand when dry to smooth and redo at any time.
Patience is your friend and take your time.
When you tape off the parts you don't want plasti dipped, use a sharp razor around the edges of the tape so you don't lift the plasti dipped part you worked so hard on.