My first time with 476 was a nightmare. I applied it to the whole car before buffing off, and was left with a rock hard solvent-style wax to buff off. Hardcore.
Do
one panel at a time. Allow to cure for a few minutes, then buff off.
476 is amazing, don't get hyped into buying 915 unless you want it. The beading on 476 reminds me of the T1000 from Terminator 2, its like mercury moving around your when you drive off.

As for 915, its just got more carnuba in it. I read that it gives
slightly better shine than 476, but most people won't able to tell the difference on a well prepped vehicle. I will be sticking with 476 myself - its cheaper but 99% as good (IMO).
As for 815, I use optimum spray on wax in-between 476 sessions instead, and its awesome. Very high shine.