If you have an airbrush, the best paints to use would be ones that are specifically designed for fabric. Createx makes a line of ready-to-airbrush colors. They're pretty inexpensive, and can be found at most larger hobby stores (Ben Franklin, Hobby Lobby, etc.)
If you have no airbrush, I would recommend using acrylic sprays--not enamels. And like others have mentioned, mist the paint on (whichever method you go with), don't spray too close.
I agree with everybody else. If you have to use a spray can, be very carefull or you'll end up getting black speckles all over your boots. might be a good idea to practice on something else like an old pair of sneakers before you try it on your CAs
Yeah. I have more or less the same advice others are offering.
If you are using spray paints make sure you practice so when you start spraying you don't have spots that are saturated or darker than others. You're misting basically not painting. Also, if you have an airbrush investigate the fabric paints. I used something similar with my airbrush when I helped a friend redesign a messenger bag of hers.
I mixed a little dark blue paint(whatever paint) and some brown and washed that over the grey part, then a lighter version over the black parts, an off-white, yellow colour on the soles (washed, not really painted on with a brush or anything) and then finally some silver spots on the stripes.
and then misted them with grey, black and brown, wich kind of blends it all together and makes the silver look un-silver like, but gives the nice spotted effect they imo, should have.
I did much the same-airbrushed with a fine mist of matt black and a magic ingredient-strong cold tea!! Did the tea thing on the flightsuit too, works a treat and doesnt wash out easily!! Also dyed the side pockets using a strong tea solution from grey to the light tan for ROTJ.