I won't check in a painting for sure if it's just packed in bubble wrap. If the painting is of any value I'd use a professional service: they'll use a wooden box for shipping and will take care of insurance. Such a service is rather expensive though. Otherwise I'd try to get a wooden box myself and check the painting or call LH in advance and ask them if you are allowed to bring it on board. I'd more concerned about the Canadair flight.
Good luck!