This video demonstrates the forward sweep and the reverse sweep, emphasizing that the power for these strokes come from proper torso rotation.
Forward Sweep Stroke
The forward sweep is mainly used by solo paddlers to turn the boat to the off side, although a partial forward sweep can also be used to turn a tandem canoe.
It begins with your blade planted in the water far forward and with your shaft as horizontal as possible. To do this, your control hand gets held low in front of your stomach and the shaft arm is fully extended. With your blade planted firmly in the water, sweep as wide an arc as possible out to the side of the canoe, finishing the stroke just before your blade hits the stern.
It will probably come as no surprise at this point that the power for the forward sweep stroke comes from torso rotation. In order to encourage this, you can watch your active blade as it passes through the water.
Reverse Sweep Stroke
The reverse sweep is another stroke mainly used by solo paddlers to spin the canoe, although a partial reverse sweep will also get used to help spin a tandem canoe.
The reverse sweep is as simple as doing a forward sweep in reverse. Plant your paddle as far back as you comfortably can while keeping the shaft as horizontal as possible. This will mean keeping your control hand low in front of your stomach and reaching with your shaft hand towards the stern.
During the windup for this stroke, make sure that you rotate your torso aggressively to keep your hands within your field of vision. With your blade firmly planted, you'll then unwind your torso and sweep as wide an arc as possible with your paddle, keeping your hands low the whole time. The stroke ends just before your paddle hits the bow of your canoe, having completed almost a 180 degree sweep. Like the forward sweep, your arms stay in a fairly fixed position while your torso does all the work.