I was taught how to detail when I got my Golf detailed and was told the following:

- Use a 1:10 dilution ratio with water being the greater constituent in the mix.
- Turn mixture adjuster on the lance all the way clockwise (or anti-clockwise, I can't remember what way exactly) until it can't turn any more. And then turn it the opposite direction by one full turn. This should ensure the best snowfoam / water mixture. Have a try and see what way the adjuster should be turned on your lance - it should be pretty obvious which way is correct.
- Spray onto car without any pressure washing beforehand. If you pressure wash a very dirty car, the high pressure water can score the paintwork by moving dirt particules along the paint.
- Leave to drip until no foam is left (circa 3-5mins). During this time go round all wiper blades and panel gaps with a soft detailing brush to rid them of any built up dirt.
- Rinse off with high pressure water.

This advice came from arguably the most respected detailers in the country

Hope this helps

Cheers