As Ekona and Downhuman have said, I can't add much more to that.
Trial and error on what works best for you really, I don't even dare think about how much I've spent on detailing products though.
I've not tried Ultima but I've found Tough Coat and Werkstat Acrylic to be very similar. I was using EX-P on my Azure this winter but that was replaced with the Werkstat at the weekend as I had some left over from when I had my silver Impreza. I tend to favour a wax over the summer months on the Zed though so may look into Ultima for next winter.