Detail Master does carry flocking in a variety of colours. Basically you would put white glue (Elmer's or the like) where you want the carpeted area, put some flocking on there, wait a bit then flip the piece on its side, tapping it gently to knock off the excess. The glue will dry clear and if you make a mistake, it can be washed of with water.
Here are some links to a couple of tutorials:
http://www.briansmodelcars.com/tutorials/tutorial/75
http://www.briansmodelcars.com/tutorials/tutorial/39
http://www.briansmodelcars.com/tutorials/tutorial/8