This was actually fairly difficult, mostly because the information on the internet was outdated. This is just one way of initializing CAN. I chose this method because it does not require re-compiling your device tree.
I may post another article that shows how to accomplish this via a rebuilt device-tree, which will ensure that CAN is available at boot without needing additional startup scripting, but I’m still working out the best recipe for that. Again, the internet resources are badly out of date wrt the current Debian image.