The point of doing it immediately, is so you're not rubbing contaminants into your paint and sealing them in with wax. I wouldn't really recommend doing it after a couple of days, unless you have some way of assuring that the paint is still free of any contaminants that won't damage the paint when you wax it.
Agreed, you really need to wash, dry and then wax. I have spent as much as 8 hours washing, drying, claying, cleaner wax, sealant, carnuba wax.............. :-D It's a sickness...
I like Meguiars NXT 2 does a good job of shining but in my experience doesn't last very long. About 3-4 weeks in the Florida summer. My current favorite product is Blackfire Wet Diamond.
What they said with an exception; if your car is not heavily soiled, you can use a quick detailer spray to get it clean, and then use the wax. I like the Eagle One quick detailer.
Depending on the color you have, turtle wax has the "Black Box" for black cars...all I have to say about it is DAMN It hides swirl marks and light scratches really well and when the sun hits it you would think that a sheet of glass is all over the car
Also a MG Product User
Meguiar's Gold Class Car Wash Shampoo & Conditioner
Meguiars GOLD CLASS CARNAUBA PLUS CAR WAX
Meguiars Hot Rims Meg & Aluminum Polish
Recommend waxing after washing as well, unless you run your hands down the paint and it feels a little gritty, then I'd clay first.