There are several ways to my knowledge on how to get trims restored. Applying a product on top of it might or might not work. Depends what sort of damage the trims are in. Some have even managed to restore trims simply using a heat gun to re-melt the top plastic layer (search in Youtube). Tried that myself and is a little risky with a knack to getting it right. If plastic is flaky and brittle little that you can do.
Products that I know of to restore trims:
Spray on plastic trim protectants. Hides/restorer the damage to the plastic trim a little. Works if damage to plastic is minimal but doesn't last long. Tried Optimum opti-bond tire gel which works on mildly faded trims and gives it a nice black sheen but being water based it gets washed off a bit with rain/car wash. Tried Einzett plastic/rubber protectant which works well and last a little longer. There are also OTC likes: Meguiars, etc but durability is about the same.
Resin based trim restorer which lasts much longer than those spray ons, can try Soft99 Black parts one. Cost <RM50. Available in most supermarkets and Autobacs.
BLACK PARTS ONE -Unpainted Resin Parts Refresh Kit- | Coating Agent | Exterior Car Care | Car Care Products | SOFT99 corporation
I've also tried Dodo Tyromania which is a wax for tire/trims. Works great but needs a knack to applying it properly without wax streaks.
There are also trim coatings out there but would cost a bomb (Dodo Supernatural gloss/satin trim sealant, 22ple plastic and trim restorer, CarPro PERL, ... etc)...
I would go for the Soft99 Black Parts One as it is affordable, available and lasts longer than those spray ons.