After 40 years of training in Kali/Silat with heavy influence on blades, I have never taught knife defence. We do lots of flow drills, but realistically they are just working for a combat stress response or, simply put, reflexes. Do they work? Who knows? I have only been attacked by blades at work.
@Oldguyjiujitsu a six-foot handrail? It would have to be in your hands at the time of the attack, and you have to hope you aren't battling someone with extensive experience with a knife. Mind you; I would rather have the staff or stick or, more preferably, a Bolo.