I haven't found any product or paint, all brands of flat and types (enamel etc.) that has satisfied me.
I use an India Ink wash of about 10 or 20% that does the job for me. I do tend to be heavy with it so this really stands out. I'm pretty sure I used water to dilute, possibly some flow adjuster or soap. I have one of many bottles I mixed and tried and the one that works stays in front but, of course. never wrote down the exact formula. It's a generous bottle so will last me quite awhile.