I think the 'clear coats' applied at the factory has been the biggest improvement in auto finishes.
What I do that is very simple is- use a waterless wash & wax with a micro-fiber towel.
I have used 2 bottles in last eight Months / actually kind of therapeutic.
For the black plastic, I use a High-Gloss Vinyl Shine.
In Winter, if covered with road-salt, I go to a self-car wash just to keep it looking decent.