I've never personally used that primer before, so please take the following advise with a grain or two of salt...
I've used Simple Green. It's easy to get (in the US, at least) and is gentle to the plastic miniature. I just pour some in a small cup, drop the figure in and let it set for 24 hours or so. Sometimes longer depending on how thick the paint is. Then I get out an old toothbrush and a couple of toothpicks and get to work.
http://www.simplegreen.com You can get this pretty much anywhere (Target, Wally World, Dollar General).
I wouldn't risk anything stronger than that or poor Luke might end up looking like his dad (minus the armor). Hope this helps.