The best and easiest way to clean the hull is with Castrol Super Clean, I would dilute about 50%, elevate the ski, open the drain plug, spray it on, let sit 5-10 mins. and hose it down. Just use a garden hose, if you use a pressure washer you stand a risk of getting water into the electronics. It does a great job, your hull will look like new.
If you can't find the Castrol Super Clean, I've had good success with Purple Power also.
Lou