Too broad of a concept to have any real value -- shaping tools aren't plastic, they're usually metal. Used properly, a lot of metal scrapers are good for cleaning and planing fbs in really bad shape. I use a razor blade in a specific manner in the late stages of a refret job, and recently used one to clean a really, really awful fb. If a credit card works for you, cool.
Well, don't be -- that's simply not the case. There are nearly 200,000 members of this forum, and I doubt you can find any that would tell you that that is, in fact, something to avoid. The awkwardness of trying to clean the fb with the strings on might also be why you ended up scratching your fb.
Not sure where you read that, but I've used it regularly on dozens of instruments I've owned over the past 10-15 years, never had a problem. Note that we said 0000 steel wool...if you don't know what that is, then don't try using steel wool because there are types of steel wool that will scratch the hell out of the wood, and that would leave you buffing down for quite some time.
OR
You could also go to the Ernie Ball site and follow their recommendations for cleaning and caring for your bass's neck. They are quite detailed in products and steps.
Cheers!
ltt