The Zaino recomendation for using Dawn is a one-time only thing meant to remove any other products that you may have used on your car. It is not meant to be repeated. That said, claying will do the same thing and is a good step to include in your process before applying any polishor wax. I think using a quality microfiber towel is fine -- I'm not sure you can even find a 100% cotton made in the USA towel these days. The towels (blond and white) that Zaino has on their website sometimes are excellent too. I have a pack of each and really like them.
2011 528i (ED 6/1/11; USA p/u 7/23/11) Space Grey / Black / Light Wood / Sport Auto / HUD / Packages:Premium & Premium 2 / Sport / Drivers Asst
2006 325xi / Sparkling Graphite / Terra / Walnut/ Steptronic /Premium Package - Nav / Xenons || iPod Adapter | Blacklines