Use SEM colorcaot or VHT Vinyl dye. We use SEM colorcoat @ the Uphostery shop.
http://www.sem.ws/category.php?category_id=36
To prep the surface, strart with a good cleaner. I use Auto Magic's special cleaner concentrate (number 713)
http://www.automagic.biz/cleaners.htm
Follow this with a good wax and grease remover. This wil removew the wax, grease, and armor all...a lot of the hard to remove things that can screw up an uphostery/dye job on a dash or panel. For vinyl, follow this with Vinyl Prep via package directions. SEM makes a very good Vinyl prep availble in a qaurt or a spray can. Sometimes a second application is requires depending on the panel and it's condtion. After this the Vinyl panel is ready to spray.
For plastic, follow the wax and grease remover with a plastic prep (SEM and Dupont make good ones.) After this sand the plastic with a 400 grit sand paper. Follow once more with Plastic Prep. At this point you have a few options. YOu can use ONE of the following...DO NOT use all on the same job.
You can use
a)Adhision Promoter, SEM makes a good one
b)SEM Flex Bond
c)SEM Sand Free
I usually use the Sand Free or the Adhesion Promoter. Apply what you choose via package directions. Now your ready to re-dye your dash and panels! Use SEM Colorcoat or VHT for the Vinyl (I use SEM), use the SEM (not the VHT) for the Plastics. If you do it right it will turn out very very well.
SEM is around $8-10 a can...you can follow it with one of the 3 SEM clears for added protection or a change of sheen/deepen the color. I usually use the Satin Gloss Clear.