I think a J stroke is more effective as a leisurely stroke, such as for trolling when fishing.  I use a very short J at the end of my stroke, just a little 1/4 flip at the end of the stroke as the paddle is coming out of the water for the next stroke.  It is also useful when paddling tandem and your front paddler is not quite as strong as you are.  Then I'll do it every second or third stroke just to maintain direction instead of ruddering to adjust.  The trick is to adjust often and not wait until the canoe is beginning to noticeably veer off course.
Now I exclusively kayak and use a double bladed paddle.  A kayak paddle allows you to take an extra power stroke (or 2 or 3) to adjust direction and not have to rudder at all.  I have found going back to a canoe paddle uses a whole different set of muscles than the double bladed paddle does.