Yep, swirls marks are inevitable but black looks awesome when clean (biased, but it's true ).
For applying by hand, I've got Autoglym Ultra Deep Shine which contains fillers for masking swirls and very fine scratches. I then top that with AG Extra Gloss Protection, which is a sealant. There's also Poorboys Blackhole which is a glaze that contains fillers too. That works really well on dark paint.
A pressure washer is an important bit of kit to rinse the car first and try to remove as much debris as possible to avoid dragging it over the paintwork with your mitt. Oh, and ditch the sponge if you have one, and replace it with a microfibre washmitt.
In tha past I would normally use a meguires microfibre wash mitt and the two bucket method, but now think that microfibre is too harsh and am considering getting a lambswool mitt instead. I would normally use autoglym shampoo at this stage followed by:
No, not every week. I polish as little as I can - 2 or 3 times per year. AG UDS (and SRP) are not particularly abrasive but because they have abrasive qualities I try to do it as little as possible. I do a machine polish once a year, (maybe twice) but use Menzerna polishes as they're better for machine polishing.
Basically, if I was wanting to polish, my routine would be - snow foam, rinse, wash, rinse, clay, wash, rinse, polish, sealant, wax. For a weekly wash, it'd be snow foam, rinse, wash, rinse, Quick-detailer spray or wax top-up.
You can leave the sealant as the final product but I tend to apply a wax on top, just for extra protection really.
Yes, I'd get a decent towel - water marks will really ruin the finish. If you keep up the wax protection, run an open-ended hose over the car and it'll aid the drying process, which means you'll just have to pat the remaining water droplets.
My A3's half leather and recently bought an X5 with full leather so also looked into leather care. Heard AG leather care was good but if anyone has any scuffs or cracks I've heard glowing reports off the bmw forum that www.liquidleather.com is really good. They have a scuffmark pack that they can clour match the leather with model of car you have.
Prevent the sunlight. Whenever you are not driving, or your car is going to be in sunight, place a sun blocker in your windshield.
Purchase or rip old t-shirts to shreds. Auto shops such as Pep Boys or Autzone offer t-shirt fragments that you can use as cloths.Buy security. Leather conditioners can be bought on eBay, at Pep Boys or even at Autozone.