1) What's best for dusting?(yep mine's Black)
2) What's best for getting scuff marks off plastic?
3) Anything wrong with using a chamois cloth on any of the surfaces when I'm being obsessive in cleaning stray marks?
Regarding dusting, I've gotten hooked on the California Car Duster. I bought mine at Sears for about ten bucks (on sale) -- works great. Be sure you follow the directions regarding prepping the duster -- it's got a lot of paraffin wax in it at first.
Not sure about getting scuff marks off. I'm sure somebody else will help on this one.
For fingerprints, etc try using any touch-up spray like Meguair's Final Inspection or Mist N' Wipe. I like to use disposable cotton wipes with this type of product to avoid any possible scratches. Try one of the forum sponsors, Meguair's or Griot's Garage for these types of things.
As Nick implies, it is best to use the California Car Duster (particularly when new) when the car's surface isn't that hot and in the shade, otherwise you could get some wax from the bristles melting onto your paint and leaving streaks. A lot of people like to use it before leaving rather than when the come back for this reason, but you can use it whenever you want of course.
The common advice is to leave your duster on a pile of newspaper for a few days when it is new.
Use very light pressure. I just let the weight of the thing do the job.
For dusting I stole a box of my wifes Swiffer cloths. I've found these to be great for picking up the dust. I use the non-scented and ridged pattern variety (the ridges help prevent scratching in case there are any minute hard & sharp particles). I just lightly drag the Swiffer across the bodywork and let the static do it's work. Just watch out around the door locks and other metal areas, as I've received a few static shocks for my troubles-eek-
A company in Batavia, NY makes a product called tha Kozak Auto Drywash Cloth. It's a treated dust cloth used by most high-end body shops and detailers. I've used them for years. Their phone number is 716-343-8111.