One method is to use velour flocking that is used in the plastic modeling hobby. They use it to simulate velour seat covers, carpet, etc. The particular product that I used to restore my '70 Chevelle console was from Detail Master. It should be available from any decent Hobby Shop that sells plastic models. I have never seen it at Hobby Lobby or Michaels (Houston area).
You can purchase it online at
www.detailmaster.com . The only problem is that it is sold in small quantities,so it can be expensive. I used approximately 8 containers of it. You will also need aerosol glue. It comes with complete instructions on how to apply it and it makes a seemless velour coating just like the factory GM finish.
Good luck, R. Garcia