Of all of the creative steeping/ageing/mixing processes I have heard, the bra method is my preferred way.
But, since I do not wear a bra - I'm a guy - then maybe this will work: Robart Paint Polish Shaker Battery Powered 410 | eBay
Seriously, I am a CP and UC guy.
(Inside my pickup truck hubcaps and a bumpy gravel road is probably second best to the bra.)
The hubcap method would be a lot more cost effective than finding a mixing/steeping mistress!