One thing I love about your humor, Mr. Stoker, is that you are so Britishist. But sometimes I have no idea what you are talking about. What is Dulux Once?<br />
I'm gonna guess it's the soap your mum washed out your mouth with! Bad boy!
It doesn't refer to coats of paint, the 'once' thing is how many times you can use that brush before the paint refuses to wash out!