Ahh I getcha, thought you meant interior trim /ubbthreads/images/graemlins/banghead.gif Eastwood make a paint for that. Also you can make the plastic/rubber trum above the door skin look like new with a cutting polish, aswell as any plastic/rubber exterior trim. I would stay away from mat black though, weren't they origionaly a semi-gloss?
I think you mean the window frame?
My advice is as follows
Wet sand the black with 500 grit don't try to rub through to bare metal though all you want to do is give the new paint something to stick to.
Clean with Prepsol/wax and grease remover.
'If' you do rub through then spray a mist of etch primer over any bare metal spots then spray them with a primer, The primer can go on over wet etch (wet on wet). Rub down with 400 then finish with 500, clean with Prepsol/wax and grease remover and spray.
To spray try to have the car in a garage, and use a heater to get both the surface and the air nice and warm, make sure there is no dust floating around too. Also make sure there is no dust on the car as the air stream will move it around. Obviously you will need to mask very well.
When spraying (with Aerosol or gun) start spraying on the masking moving onto your work (this is so you don't get a splatter of paint) moving back and forth with nice even strokes, each stroke should overlap, I was tought 60/40% overlap. About three coats, first is a light coat called a tack coat. I would personaly use a clear over top (it will be shiny but that is a good thing isn't it?) Time between coats is how long it takes to work around the car so you pretty much won't be stoping, wait about 30min before doing the clear. If done right it will look real nice and you won't need to polish it or anything. If you don't use a clear then the cleaning and spraying is still the same.
I'll try to find a link that explains it better than that though.
I'm doing the same thing to my car, I'm going for a high gloss as I think it looks good.
Are your trims just faded? any chips? rusty spots etc?
Ahh very important when spraying, cover all the paint on the car, spray sits in the air then lands on everything, afterwards you will rub your hand on the car and it will be all furry.
Maybe that helps