Go Kiwi roads! :teeth: Extra slick, because over summer it actually gets reasonably warm here. Saw this the other day, had to watch again, just because.
When I purchased my Z over 9 years ago, I had to sign a form at the dealership to say I didn't want them to clean it. Never regretted that for one second.
As most have already commented, the one thing I will add is, you've only just purchased the car, which means you don't know it's full history. So it probably wouldn't hurt to give the Z a full service.
I have used our Stihl water blaster on roadsters before, but having said that we had 2 nozzles especially made as wasn't happy with the stock one. Take it very gently.