Yes...I have. I used 2 part marine epoxy. Since it's a putty, it's easily molded and stays in place. I built it up just a tad higher than I wanted, and then sanded it down to perfection once it cured.
Since the only color I had in stock was a burgundy, I colored the final product with a black sharpie. Although the patches are not perfect to the eye, they are to the hand.
Perhaps there is a better way, but this worked for me.
On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"
'68 Sprite 1275
'76 Midget 1500