Car covers are good for long term storage. The car needs to be spotless clean as well as the cover. Take your cover to the laundry mat and clean it. Use a very small amount of soap. Remember, you are just washing off the dust that has settled on the material. Do not use fabric softner or dryer sheets. These products will leave a white film on the paint over time.
Car covers, no matter how clean the car or cover, WILL scratch the paint. Make sure the paint is cool to the touch before putting your cover on. Warm paint is more prone to scratch then cold paint. If your car is a light color, then more frequent use is allowed, because the "average" eye will not see them. Always keep the paint waxed. Make sure your "wax job" is fresh before putting the cover on. This will aid in knocking down the amount of scratches you will get. Once the cover is on try not to disturb it as much as possible. If your car is a dark color scratches will be apparent. It is recommended to never put a car cover on a black car.
Car covers purpose is not to keep dust off the car; (although it does do a good job at it) is to protect the car from anything that may come into contact with the vehicle. Bumping into it, animal walking on it, bird or sap droppings if outside, setting something on the car, etc. Its first and most basic function is to create a layer of protection for the cars surface against contact.
Always wash a wax you car in a cool setting. Never in direct sunlight. Make sure the paint is cool to the touch before starting. Apply your wax with a small damp piece of sponge. Do not use the terrycloth pads that can be had at the local parts store, they will scratch the finish.
The duster idea although handy DOES scratch the paint. They will tell you till they are blue in the face that it does not, but it does. Yes static picks the dust up and away from the paint, but the rub factor is still there. If your car is dusty and you touch it with anything it will scratch. If you rub a small spot on your car with your finger you have just scratched the finish. This is why it is sooo important to keep the car with fresh wax on it. It gives you another layer of protection for the clear.
The detail spray is also subject to the same pitfalls. Remember you are rubbing the surface after you spray. So essentially you are rubbing the dust into the paint. The detail spray is designed for quick clean ups of hazards that are worse then the spray and rub you are about to do. IE: finger prints, bug guts, or bird droppings that my have occurred on the way to the show/cruise night .. etc.
Blowing the dust off is an easy and relatively safe, but ineffective way to get dust off the car. It does have some fall backs as well. First is the fact that not all the dust is going to come off. Blowing with compressed air will leave a "zebra" type effect. It will only remove the dust from the exact area that you are aimed at. So for example: you blow your hood off. You move the blower back and forth say 5 time. You will have 5 really clean stripes and the rest will only be slightly clean. This will be very visible with the naked eye. The dust you are blowing from your direct path will only land somewhere else on the car. The dust will not "just blow off". The dust is actually settled into the fine microscopic scratches of the paints surface. The dust; as a general rule, has a DC negative charge,as where your vehicle has a positive one. This will make the dust sick to the car. Making blowing it off a very difficult thing to do. This can be proven by driving your dusty car around the block or even down the expressway. The outer layer that was only on the top of other dust particles will come off. But the car will still be covered with dust. The other fall back and most crucial is the fact that you are shooting it with compressed air. 125-150psi if your using an air compressor, 6-15 psi if you are using a leaf blower. I would be leery of it picking something up and shooting it like a gun at the car.
Washing the car has been and is still is the safest way to clean and remove dust from the paint. The water gently washes away and dilutes the dust with very little to no repercussions to the finish. Although, the most time consuming. A nice light dusting of water over the entire car, then a power rinse will remove most of the dust and dilute the rest before you start to wash with soap and water.
Bobby
20 years in the body shop industry
32 years going to car shows
4 concourse 395+ point cars
countless other show vehicles
Numerous restorations and race car projects
Judge: AACA, Studebaker Nationals, ATTCA
and a REAL picky father