I tend to stretch more formally for surf kayaking, whereas with regular touring I limit stretching to a few easy-to-do basics. Any elaborate stretching regime is bound to fizzle out unless one is extremely disciplined individual, so keeping it simple usually has real-world value.
For shoulders I simply place my arm around my neck making a hook, then gently forcing the bicep of the arm thatís around the neck further under the neck using the opposite arm and hand to generate the force, producing a good stretch. The other classic stretch involves taking one arm up over the shoulder and placing the hand of that arm down the center of your back in-line with the spine, the pushing downward on the elbow thatís pointing skyward using your free arm and hand.
Limbering your torso can be done by placing your paddle along the top of your shoulder and turning both directions from perpendicular as far as you can, this being done in the boat. You can also take one arm at a time and reach around as far as possible to touch your hand on the rear deck. Depending on the height of your cockpit you can alternately lean forward and backward as much as possible, bending to the maximum.
Do all stretches slowly and hold the stretch the moment you sense tightness. Wait until the tightness dissipates, then stretch a little more, continuing until the full stretch is achieved.
I also like to stretch the hamstrings and calf muscles and the most effective way Iíve found is lying on my back raising one leg at a time, using a towel to pull, while the calf stretch is done pushing against a wall with the ball of my foot on a two inch book, again done only to the point of feeling the tightness before proceeding.
Wrists are easy enough to stretch by placing your arm straight out and using the free hand to pull the hand backwards (hand is straight out like youíre stopping traffic); then flip your hand 180 degrees downward and pull toward you with the free hand. Thereís variations and additions on all the above; nothing beats regular Yoga or other regimes for general maintenance and as a pain/injury preventative.
I've had a number of shoulder surgeries and know how important one's shoulders are to a paddler. Individuals with specific pain and overuse injury should consult a reputable clinician or sports specialist for care and on-going treatment or advice.