You demonstrated your ‘trick’ when painting backgrounds by painting a brush loaded with water across three or four colours. Your colours dry without being muddy. I have tried this, but my colours always look muddy….what am I doing wrong?

It could be that you are brushing the water too hard (pressing down so that the colours are spread into each other too much), or perhaps you are taking too long at this process (you have to work quickly). Practice a number of times to get just the right pressure and the timing right. It works for me, so it can work for you.