How to make a Wash

I've painted a lot of Nurgle themed models over the years. Every time I start one, I do it in the same way - white primer and a special wash. This wash changes colour with every batch, but it always works out.

I've been asked many times how I make the wash, and I can never really explain the exact method. This is why with the latest batch of Nurgle Wash I decided to document it so I dont have to explain it every time :)