Oh boy, lots of opinions here. A fair amount depends on the current condition of the paint. If in decent shape, try a fine hand polish (I use Griots, but there are quite a number out there, but use something pretty fine). Try it in an unseen section to gauge how it might affect the paint - ie. does the cloth come away in body color?? If the paint is in good condition, the very fine hand polishes (AutoGlym is another I have used) should do a very nice job. Just take that part slow and easy. My 280 SL has a couple of panels that were painted early in its life, and the paint there is a bit iffy, so I generally just use wax. The original panels are holding up well.
Then you can use clay to clean off the finish (this has been mentioned on the site - so the search function should yield some comments). It is amazing as to how much stuff the clay picks up from the finish. After using the clay (again, a number of manufacturers have this - I have used Griot's) the finish is as smooth as glass, and rubbing your hand over the parts you have not used the clay on is night/day.
Once done, use a good wax (again, your preference, here I have used Zymol products). And get out there and enjoy.
Generally I do the clay once a year, wax maybe twice.