Before I wash and sand them, I usually take them to the power washer. That tends to take off all of the texture that is flakey. I havn't ever figured out how to get the texture back on the parts again. Seems that once they are scratched and flakey, I can't get them to look original again. If all the texture comes off, I just paint them with flexible primer and vinyl paint and they come out looking ok. Not original texture ok, but just a decent looking panel until I can get a perfect one.