Do these diffusers require drilling or modification to the rear bumper?

No drilling required. These mount using your vehicle's existing rear bumper attachment points. Before assembly, verify your bumper's hole pattern aligns with the diffuser mounting tabs — minor fitment tweaks are normal during initial install.

What prep work is needed before paint or coating?

Sand the surface with standard automotive abrasive and wipe clean with a tack cloth. Apply your chosen epoxy primer, let it cure fully, then sand again before topcoat application. FRP accepts single-stage urethane, base/clear, or vinyl wrap equally well.

How do the two pieces separate, and can I install them one at a time?

The diffusers split at the vehicle centerline. Yes, you can install one side first, verify fitment and gaps, then bolt the second side. This staged approach helps dial in alignment before final torquing — refer to your vehicle's service manual for fastener specifications.