I used a couple of the black shades last night, one was completely fine, the other one was a nightmare. Something to look out for is the drying paint around the lid and lip of the pot flaking off into the paint, as well as bits thickening up into lumpy blobs in the bottom when the paint gets a bit old. Teabag paper straining would sort it, and I agree on the LC thinner, plus retarder. In the end however I went to Tamiya for the second shade, and it was 100% perfect even though that was an old jar too... Sometimes you wonder if some paints are worth the trouble.
There's always a bubble when you open the lid too!!