There are two trim dressings available......the Super VRT and In&Out Spray. The VRT is for Vinyl, Rubber, and Tire, hence the acronym but it can be used on plastic. It is designed to penetrate and condition which it cannot to with plastic so I tend to not use it for a cure all when it comes to hard, non-porous materials. The In&Out spray is better suited for plastics but since it's an aerosol, containing it to smaller trim pieces, especially on the interior, is difficult. You could spray a little on a small applicator and apply it before it evaporates or another similar technique.
Adam's also makes a product called "Quick Sealant" which is for paint and exterior, but I've found that it provides a great medium style sheen to exterior trim pieces. I'll have to give it a try on some interior pieces and see how it does. Again, since it's an aerosol, you'd need to spray on an applicator of a suitable size and shape and then apply it to the desired area.
