OK, new paint answers.
Washing, yes, but use very mild and gentle techniques. Deffo two bucket method..
Polishing - NO, NO and NO! Polishes contain cleaning agents as a minimum and will damage/mar new paint.
Waxing - Yes, BUT, it MUST be a pure wax, eg Natty's blue, Nattys, Pinnacle Souveran, etc etc. A pure wax does not contain any abrasives and so will be fine to use after three weeks curing.
Hope this clarifies?
Any Q's shout!
Iain