I manage a fleet of vans and have to do this every time I sell an old one.
Usually a heat gun and straight razor works. Not a blow drier but a real heat gun - they're cheap.
If no go with that route - older and drier, brittle stuff:
Use 3M "woodgrain and stripe remover"
http://products3.3m.com/catalog/us/e...er/output_html
Spray only on small area at a time, let it work and scrape off.
Then use the adhesive remover if you have sticky stuff left over:
http://products3.3m.com/catalog/us/e...eme_us_aad_3_0
Other products are here too:
http://products3.3m.com/catalog/us/e...er/output_html
I have found that most auto parts stores have one or two cans of each of these or can get them in a day or two.