Sorry for not responding sooner. I don't usually get much time to read everything in all the forums, so your best bet is to email me directly.
I thin the Citadel inks with water, most of the time it's distilled water. Once the ink is down and has dried, you can remove it with any ammonia-based glass cleaner, I typically use Windex or some generic blue cleaner.
What I have noticed is that Windex on a clean brush allows you to blend colors nicely, and can remove the ink even from uncoated flat paint.
Hope that helps!
Jeff