What you need is not paint, use stuff from autobarn VHT colour dye (should be in the same section as the engine enamel, chrome paint etc..).. works great, and i'd only sand it if your current dash trim has got scratches, paint worn off etc... Just make sure you make heaps of coats, depending on what colour you pick it will be harder/easier to get to look bright, as its not a paint its a dye.
I used it on my old charade and came up a million. B) Red dye over black plastic, no sanding, just a decent cleanup with wax and grease remover.
Sorry thats the only pic i could find, and yes, its the same stuff i used on the vinyl to cover the door trims (they were red vinyl but could not leave them like that cos the vinyl itself faded to pink!! sprayed that stuff on and stayed red).