1-Raggtopp protectant for your canvas top and look into getting a soft top cover if you leave your outside for more than a few hours every day.
2-on dark paint
I dont AT ALL recommed any car duster.
Basically with an quick detailing you only want to do it when the
both the paint surface and the towel are wet/damp.
The most professional way to dust off a car is to use a quick detailer
FK #425 (keeps the surface too slick for dust) and a waffle weave towel (just got some very nice towels from
www.poorboysworld.com. Mist the entire panel and the towel and use downward strokes. Flip the towel with each pass so that you always have a clean side touching the paint. and try to minimize the number of passes across the paint.
Allot of pros that I know will never dry a car without first lubricating the paint surface with a quick detailer like Mother's or Meguiar's. Makes sense.
And don't quick detail often. It will micro marr your paint.
For non-quick detailing (when the paint is just washed) i use this:
Poorboys Mega Towel 12 for $48 (best towel I've seen so far)
p.s.
here's a good page on washing your car
http://www.paintcare-n-detailing.com/