I use a Dyson and a new painter's 1" brush and common sense. Open case, disconnected from 'mains', hold vac nozzle a safe distance away while gently brushing off dust from nooks and crannies. To clear dust fluff balls from CPU cooler veins then invest in an artists set of brushes. If you need to go down the anti-static route then simply discharge yourself with the stainless steel basin first.
I've been taught that the safest way is with compressed air. Just hold the fans (antistatic precautions required) to stop them spinning (act as a generator and can blow sensitive circuits, as I know to my cost!).
I favour the paint brush and vacuum method - doesn`t redistribute dust like compressed air. I also found a hose attachment for cleaning radiators that provides a smaller nozzle for getting into the crevices better. Source was Lidl on offer some time back but they may be available elsewhere.
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