Note that the steering oar is used within a fairly small arc: You never go to extreme angles with it. If you need more steering effect to come about, take multiple short strokes with the windward (but soon to be leeward) oar, with the blade out of the water on the return stroke. The motion with your hand is a tight circle, and you are pulling at the top of the circle (blade in the water) and pushing at the bottom of the circle (blade in the air). One great thing about this is that it works even if you lose forward motion (are in irons) so you can't get stuck unable to turn like you can with a conventional rudder.
Here's Rob in 2 short videos using the steering oar to come about in a long canoe: Click Here
Two steering oars: In strong winds with a boat that has 2 steering oars, we almost always use just the oar on the downwind side (same side as the sail) and leave the other one alone. The one exception to this is when we come about, we put a hand on each oar, using principally the oar that is on the upwind side for steering, but of course within a second or two that becomes the oar on the downwind side. Often you can come about just by raising both blades out of the water and keeping the sail trimmed. An inflatable will spin in place quite smartly if you do this. If you find your arm gets tired with one steering oar, having two will cut the strain in half on any one arm. You won't use two at once, but you will alternate, using the starboard one half the time and the port one the other half of the time. If your boat has a grab line around the perimeter or happens to have D rings in the right places, you can make a home for the handle of the unused steering oar of the moment: Just add a loose loop of strap or rope in the right location that you can quickly slip over the handle end of the unused oar keeping the blade out of the water and keeping the oar under control and at the ready. Some of the videos below show this being done, especially two where it is noted below.
click photo to launch video
Videos On dinghies:
This is such a good one, we have embedded it here on the page. But don't miss the links to the others below it
http://www.youtube.com/watch?v=eWX9NBNwJCw Note how unused oar is kept under control by slipping its handle into a short strap loosely attached to grab line, one at the ready on each side. This is super clear also in this next video: