I'm gonna put aside the Tamiya thinner for the moment since I'm a bit wary on using Tamiya thinner with anything else other than Tamiya paints since Tamiya paints aren't really acrylic (from what I've seen from using it). Plus I wanna try and master the right ratios with water with Vallejo paints.

Let's see. I suck at measurements. In the 1/3 ounce cup, I fill it half with water, a drop or 2 retardant then I put in 4 drops of black. Stirred the hell out of it with a toothpiclk.