Try one of those electrostatic duster cloths that you use on electronics to repel dust.
Or you could just invest in a large tupperware to put over your model when you're not working on it.
But when I'm painting, I paint in a booth. So I turn the blower on about a half hour before I start, so it suck the air and dust out the vent. Then when I'm painting, the air is moving so dust doesn't have time to settle. Then I leave it running for about an hour or so afterwards to keep the dust off while the paint dries.
-Fred