I’ve just gone through my Episode One and POTJ collections. It took a VERY long time, and has put me off dusting my Saga stuff – all those annoying bits and pieces.
I just used a plain old duster and elbow grease. These things are pretty tough, so I wasn’t worried about damaging anything. Certain things like moulded cloaks took a lot of work because there are so many nooks and crannies for dust to get into. I considered just rinsing anything without soft goods, but I thought this might be a bit risky.
And it’s not just your figures that you have to clean. You’ll probably find yourself generally tidying the whole room, and certainly all the shelves, diorama backgrounds, and display cases than your figures are stored in / on.
I do it every six months or so, but after only a few days, you can see a few dusty surfaces “surfacing”