Don’t despair! The GURPS book is very good and it has a paragraph devoted to White Crane. I’m not as up on the various different styles of Kung Fu as I would like to be, but hopefully I can give you some tips that might get you pointed in the right direction.
The first and most important thing to understand when including any fighting style is the combat style is as much a part of character creation, character development, character outlook as it is about technique. With every martial style comes pieces of the culture that created it, their values and their philosophical outlook. Remember, when we draw inspiration from any culture (including our own) we always take pieces of that culture and it’s outlook with us into our own work even when it’s unintentional.
Authors that draw on Japanese martial styles or even just Japanese anime for their storytelling will bring aspects of Shinto and Bushido with them. The thematic underlay may be unintentional, but it is there. When working with Chinese martial styles you’re looking at Confucianism and the Tao. Ignore the greater parts of Asia and stick to China, study Chinese philosophy and history. I’d even throw Sun Tzu’s Art of War in there, even though that’s more for army strategy and mass conflict.
By learning about the style, it’s history and the politics that come with it, you’ll understand more about how to write the style. Look at the snakes and the cranes whose movements were the basis for these styles. Check out The Karate Kid remake with Jackie Chan which is actually a very good training movie and brushes on some of the basics of the Tao, chi, and the spirituality that’s inherent in most of the Chinese fighting arts.
I’m not a good enough Chinese movie film buff to know which of the vast collection of movies there would be useful, I’m sorry. However, I would check online in your local area and see if there are any schools that teach either of those (or if you can’t find them any of the Kung Fu styles). Martial arts schools can pop up in weird places, really, really weird places like for instance you’d probably never guess that there was a Ninjutsu school in Louisville, Kentucky (you can only get in by reference from another martial artist who goes there). The instructors who teach are usually people who are passionate about their art and passionate about teaching others about those arts, it can be intimidating to ask questions but they are usually very nice and very patient.
If you’re upfront about why you need the information and what you’re trying to learn, they’ll most likely be more than happy to help you. If they’re not, then you might be able to start a dialogue with a different instructor, even if they are cities, states, countries, or continents away from where you are. This is the miracle of the interwebs.
Just do your homework to make sure you’ve found what you’ve thought you’ve found first. It can be difficult to navigate the world between the practical and the esoteric parts of the martial arts, but they’re really not as far from each other as we sometimes think and they do intermingle.
I don’t know if that helps, but I hope so!