Do I need to modify my existing fog light holes?

Check your OEM bumper's fog hole placement before final fitting. If the cover's cutout aligns with your existing lights, no modification needed. If positioning differs, you'll need to reference your vehicle's OEM bumper hole locations and mark accordingly before drilling into the FRP.

Will this cover my parking sensor cutouts?

FRP covers come blank. If your vehicle has factory parking sensors, measure their location on the OEM bumper and transfer those marks to this cover before final installation. You can drill sensor holes after the cover is fitted and prepped.

What's the best way to prepare this for paint?

Sand the entire surface to accept primer and paint, working from coarse to fine grit depending on your chosen finish system. Follow your paint supplier's prep requirements — different primers and top coats may have specific grit recommendations. Once sanded and cleaned, it's ready for primer application.