I use Maguire's soap, but don't think there is anything special about it. I really don't believe there is anything special about any car wash soap. Just don't use a harsh detergent that will remove your wax more quickly.
I have used a california water blade to remove most of the rinse water after washing. I also use microfiber towels to final dry.
I never use a wax that has a cleaner in it. NEVER. Paste wax only. I happen to like Mother's. I'm very old school when it comes to wax.
I use the same paste wax on my wheels, both inside and out. I'm a nut when it comes to wheels.
I also clay bar the finish a couple of times per year.....love it.
Good luck with your X3