To Do the waves, i used an old knackered brush i forgot to clean properly once and it's bristles are now really stiff. I add tiny amounts of white paint at a time and just jab away at the wave tops using absolutely no skill! The crests of the waves naturally pick up the white, leaving the troughs blue. I think it works brilliantly, even if i feel like a 2 year old as I basically thump away at the base with a paint brush.