Haven't done much hands on work with textured coating, but there are a few methods that can be used.
First you want a good cleaning. There are dedicated plastic cleaning products, but you can read their msds sheets to see their makeup. I might do xylene as a first wipe, then denatured or isopropyl alcohol; & soapy water with dawn as a final.
PP is polypropylene.
High spots can be scraped or sanded off first.
There are some products I've seen, such as dash repair, that have fillers & a textured sheet to press against the surface to try to match the texture. Another similar method I've done on certain textured plastics is heating the area & pressing a metal textured item against it.
Other than that is sanding the worst of it down & respraying most or all of the part with a product such as SEM surface texture spray [forget exact product name].
Then finally spray entire panel with SEM adhesion promoter & color.
Urethane supply company is one source of plastic repair product & info. Forums for vehicles such as chevy avalanche may have some repair info
