Just the spinning metal rod? Will that make a difference? If so, please do experiment because that would be much easier and accessible than the other alternatives i mentioned, those things are ridiculously easy to get, cost as much as a couple of pots of paint (not Citadel though :P) and the little motors should be more than powerful enough for this job. In his defense, the objective of that video was to be done with the painting as fast as possible, probably for people not much into painting, and that's an odd but effective way to do it, if i recall correctly he had the slugga done in 10 minutes to tabletop level. I wouldn't do it (not sharpies at least, i've heard very good things about those Molotov chrome paint pens and might test them on something as actual pure chrome is just nowhere to be found on mini stuff) but also wouldn't discount it for others. Also, honestly i'd much rather have on the other side of the table sluggas with sharpie metallics than boring grey plastic, i've had enough of grey blobs on the table for a lifetime already.
Yeah I watched a youtube vid where a guy snipped the whisk bit off and bent the end at an angle to aid the stirring. when I get chance I'm going to experiment as I've got some ideas I'd like to try out, might even do a blog post about it (on my defunct blog) if it works out.
Badger and Trumpeter sell shakers like the milk thingies. Tamiya and Gundam sell felt pens. And those are the ones I remember, so probably many other brands do too. As for ultrasonic and other brutal methods, once I shook a bottle a lot, including sharp hits... and the damn paint went completly bad, like curd. It was fluo, so it could be anything, they are nasty from the start. Metal also can go bad in weird forms. So beware. Edit: typo.
