In the shop we used only a wrung out chamois leather. The imitation ones are fine also. Just give the pipes a good wipe, and lightly wipe the speaker fabric - this will remove any dust or lint. Then polish the pipes using a soft cloth.
Chamois leathers are great to wipe the screens on Beovisions - especially when anti reflex coated. Do this in the morning when the TV is cold. Lightly clean the screen and polish to a high shine with a soft clean cloth. NO CLEANING PRODUCTS.