Check their social media. Not just for impact play photos, but overall. The more professional they are overall, the more likely they take their craft seriously. The more likely they take their craft seriously, the more likely they took the time to master multiple aspects of the craft (including proper caning).

I would also look out for the word "disciplinarian." If they mention or highlight that, I'd assume canning is in their specialties.

I'll be honest, I'd guess only ~30% of US Dommes have this in their refined skill set. This is just from my experiences, though. I've had to stop someone in a double once because they were hitting the spine. Yikes.