Matt Russell, BMW M Brand Manager, and a BMW Body & Paint Specialist explains the paint guidelines behind BMW's "frozen" matte paint finishes. The care required is actually much less than most expect.
Only regular shampoo and insect remover (BMW recommends theirs of course) is needed. No other chemicals (sealants, waxes, polishes, etc.) are needed.
* They warn that you can even damage the frozen matte paint by using a microfiber cloth, wax, sealant, or quick detailer.