How to safely clean custom action figures

Thanks for the suggestions I'll half to try that.

As long as the customs were done well, with proper preparation and paint, I'd suggest a soft, natural hair, long bristled paint brush, 1/2" to 1" wide (I use a 1 1/2" since it happens to be what I have) for removing dust. A light brushing should be all that's needed to remove most of the dust. For more stubborn dust which has worked its way into sculpt details you can use a soft bristled toothbrush with warm, slightly soapy water per usual customization cleaning prep, then rinse off under the tap. Again, I'd say this is probably ok to do with properly customized figures, using a light touch, but if you have any doubts about them at all then maybe skip this part, non-customized figures should be fine unless they're very old and already have paint chipping off. Anyway, just sharing my experiences, having lived in a very dusty house, and cleaning figures I've customized myself, biggest issue I've had is accidentally knocking off a glued on part, which is frustrating but usually easy to repair.