Just hold it flush to the back where the fan is, do not try to remove the cover of the cooling unit. This is the only area you would possibly use a large vacuum. After looking it over, try to flow in one direction. Spray a little out of the can before you point it toward the computer. Then start on the computer in very short blasts.
Long sprays can cause condensation.
Using your electronic vacuum, carefully clean up the dust out of the bottom of the computer and surrounding area of the computer. Put the computer cover back on, carefully, and replace the screws. Take your time with this. Spray Anti-Static Cleaner onto your cotton, no lint cloth and clean the front and sides of the computer. Do not spray directly onto the computer, always spray the cloth instead.