^^
The DJ Supernatural shampoo should sud up well at that ratio. One tip for getting better suds, is pump shampoo into bucket (grit guard out) and then fill the bucket using your pressure washer lance (on lowish pressure setting) to fill the bucket, this increases the foam much more. But usually a good vigourous swishing with your hand (before putting grit guard in) as you start to add water to the shampoo, should be enough to get a decent foam. Also make sure your mitt is thoroughly saturated before starting to wash. But masses of suds is not everything, (I've used very sudsy shampoos that don't clean near as well as some with less suds), the key is lubricity, as long as the shampoo solution is lubricious (and Supernatural is), then the mitt should glide very well and smoothly over the paintwork, meaning effective cleaning with least amount of resistance/pressure required which in turn means less risk of swirling at washing stage.
Car looks great.