This was quite some time ago, so I'm not exactly sure which brand of thinner I used. I'm guessing Model Master Universal thinner is the one I used as that's the one I usually have on hand. I'm certain that I didn't use alcohol; I use 70% Isopropyl (rubbing) alcohol to thin Tamiya paints and I've had problems in the past when using this thinner as a wash, it leaves a haze. I'm sure you could get away with using mineral spirts as well if you have some around... now that all the moisture has evaporated out of the pigment block there's probably not enough solvent left behind to cause any interaction problems.