I've been using a vacuum (just the hose attachment, only use brush for case sides etc) and a long bristle artists brush (3/4-1") for years. Hold the vac a few inches away from the components and use the brush to stir up the dust. Compressed air cans work well for small areas like between fan blades or heatsink grills, just don't hold the can long in any one spot or condensation builds up extremely fast and now you've got wet dirt instead of dust.