My car is dark, so I parked it out in the sun for an hour. Then I peeled the old rear fender stoneguard piece off slowly. Removing the residual glue was a problem until I found this technique: after softening the residual adhesive with 3M Adhesive remover, use the teflon squeegee that comes in the Invincashield kit to gently scrape it off.

I am very happy with the look of the replacement Invincashield piece.