Cleaning car interior textured plastic

[LivelyMintViper]

The textured plastic that is run along the sills of the car and up the sides is a nightmare to clean. When I wash it it looks dark and shiny and clean when it dries the dirt is still there and is obviously there! I have tried using a soft brush to get into the little dents and then wiping with a soft cloth. Whilst wet it looks spotless. As it dries you can see it definitely isn't! What do car detailers use does anyone know?

My husband details and uses this. Don't be temped to get the smaller size to save money (it's expensive) as it comes in a size like a nail varnish bottle, You want the £40 one if you get it.

We have a small car dealership and my DH started as a valeter. For our personal cars we use Autoglym
Products. We use the AutoGlym bumper and trim gel. Cleans and kind of 'feeds' the plastic, protects it and brings it back to life. Will also hide any little marks or scuffs. Can also be used on any black plastic trim on the exterior, and as a tyre sheen. And it smells nice! Not too expensive.

Make sure you are not using a citrus cleaner too.

If it's got ingrained dirt, you could use a steam cleaner.
When it's dry, use Back to Black. Spray on and wipe over.
I have used WD40 before, with good results.