Oli,
I will reach in my bag of pearls and.........No wait, thats from a movie I just saw.
I usually spend the same if not more time on the interiors than I do on the exteriors mainly because the owner is in the car more than outside looking at it.
On average I spend about 2 1/2 to 3 hours on the exterior. Case in point. I did a black on black 02 911 on Friday afternoon, started about 12:45. I machine polished it with a 1200 cleaner/polish. Hand rubbed it out with cleansing lotion then applied a hand wax. Did the wheels, windows, vacuum, vacuum the convertable top, clean out the engine, front deck and door sils and I am done at about 3:30 -3:45.
The key here was knowing that the paint, while it had light scratches and some webbing, was not horrible. In fact I could of just put on a speed wax and it would of looked good, for a few days at least. So I knew that a mild polish appiled with a polishing pad at about 1200 RPM's was just the ticket to remove the light scratches, level the paint and remove any swirls. A finishing pad would of been perhaps too mild.
A going over the paint by hand, using a back and forth motion with cleansing lotion, removed any oils and residue and also ensured there were no swirls in the paint and also set up the paint for a proper bonding of the wax.
Hope that helps you out in some way.
Anthony