couple of things:
mild soap like Pinnacle Body Works or Zaino
A good sealent like Four Star UPP or Zaino Z2 or Z5, Four Star has little warmer look to it. you can top either with a high quality was for an even warmer look but the sealent will protect for about 6 months
Use a very soft Microfiber chenille wash mitt or lambs wool, or pick a super soft Boars Hair brush ($$$) but will not scratch.
when you dry use a water blade or leaf blower to initially dry...this is where most marring occurs, during drying.
after that get some good microfiber drying towels (waffle weave type) and blot the car dry, dont wipe...this will again help avoid marring.
good luck