We live in a pretty dusty part of California. I have found the plastic car covers with elastic seem to work the best. They are clear and like 20 bucks each. We keep them in the shop and put them over the car and when they are dirty just get a new one and throw the other away. The fabric ones breath and also let the dust through or when you remove the cover all the dust just falls through.
For long term storage we us the soft micro fiber kind of cover with the plastic one on top of that.
