Klasse and Zaino are my two top contenders in the sealant market of my detailing products. 3M doesn't make a polymer sealant. I find the 3M show car wax paste to be a bit oily, but it is a carnauba so you can't compare the two or try to mix the two.
Prep for a vehicle depends on each vehicle. It changes all the time. The set standard is I go by is
1. Wash
2. Clay
3. Polish (with a hi-speed rotary or a PC to remove swirls, scratches, and other paint defects.)
4. Klasse (I like to use AIO with a PC then give the car another once over by hand, sometimes if I'm in a hurry I use AIO with my rotary, then add SG.)
Klasse, I like to apply by hand.
Look into the Hall of Fame for the Klasse application guide.