This is much easier to do in After Effects but if you do not have AE here we go:
Put clip op track 1 and add Black and White effect. You can also turn down the saturation in several effects.
Put same clip (without the B&W) on track 2 and add the 16 garbage matte.
Keyframe the garbage matte over time on the car in the clip.
add clip to track 1
add clip to track 2
add a white colour matte to track 2 and add the garbage matte to this and keyframe object over time
for feathered edge add a fast blur.
Dubble garbage matte
Add RGB curves to the first clip to make the BandW more intens.
Sorry for all my questions but I'm new with Premiere CS3 and my English isn't that good.
You said in your post: "Keyframe the garbage matte over time on the car in the clip." What do you mean by this? And how should I do this?
If you watch the tutorials I linked you to you will see what you need to do.
Keyframing over time means:
You go to frame one and set keyframes for all the point in the garbage matte.
Then you go to say frame 5 and look in the program monitor which points are not in the right position anymore. Drag the point in the Program monitor to right position. Keep this doing for the whole clip
There is another way.
Put clip on track 1 and track 2
add Black and White Effect to track 1
add Chroma Key to track 2 and key the colour you want to keep.
Now add Alfa adjust effect and reverse the Alpha Channel
You can even change the remaining colour to another colour by adding Change to Color effect
Results may vary.
Well designed tip. I was going to add starting as you did, and using the Track Matte Keying, but your method is far more simple. I like that, and OP will too.
I go to Track Matte Keying 'cause I like playing in Photohsop so much, and don't get to do as much of it, as I once did.