My preference is Auto Finesse Avalanche snow foam. Loads of products out there probably better/cheaper, but it's finding what you're happy with and what fits in your routine. Get a proper snow foam lance to fit whatever make of pressure washer you have and you'll notice a big improvement from Demon.
Snow foam works great if you have a nice decontaminated car under the dust/grime. I use Fusso which holds its finish for ages, then just blast with snow foam once a week. I'm not a heavy duty detailer, but I'm sure others will tell u - never use a brush on a car. I use micro fibre cloths for washing and a deluxe drying towel for a hands on wash. YouTube has thousands of vids for best practices on wash/polish/finishing.