If our Yeti is dirty it gets washed with bucket and sponge then dried with a leather but if it's not too dirty I like using this;
I've used it for years and buy 5L at a time to refill the spray bottle. It always looks very impressive after a going over with the Williams. Micro fibre cloth is a must; one to apply another to buff; it can be applied in brilliant sunshine but I don't recommend using it on the windscreen.