Basically, if you try too hard you will go slower. WHY? Because you will use too long a stroke.
You should place the blade in as close to your toes as possible.
The start of the stroke should come from your TOES (balls of your feet), or in a moulded footrest, your heel.
As you press with your foot, you start to PUSH WITH YOUR TOP HAND.
Simultaneously, start a gentle pull with the two outside fingers of your lower hand (the one nearest the water). Outside means your pinky and the third finger.
As the stroke develops you bring the other fingers into play to guide the blade close to the kayak hull - closer to the hull the better as the hull will track straighter. Remeber, straight tracking is a function of paddling technique, not kayak. A coracle will go straight if paddled straight.
The emphasis is pushing with your top hand, not pulling with your bottom hand. Your shoulders should more or less remain parrallel with the loom of the paddle. This is where the body rotation comes in.
As the blade nears your knee, start to think about lifting it out, by the time you actually do it, the blade will be at your hips. This is as far back as you want to take the blade.
If you take the blade back behind your hips you are actually UNDOING GOOD WORK, and at the same time shovelling water uphill. Once the blade goes behind your hips you are creating drag and no forward effort, What you do get though is ruddering effect.
80% of the power is generated in the first third of the stroke. Between your toes and your knees, this is why the catch is the most important element of the stroke. Get your blade in cleanly and the rest will fall into place naturally.
If you bend your arms as you paddle you are not getting enough/any body rotation into the stroke. Think of it as stepping into a punch. You rotate your body then!
The biggest problem to overcome is taking the blade back too far. If you concentrate on one element at a time, then the entire paddle stroke will build. You have to undo the muscle memory you have built up before you can learn the new muscle movements necessary. You won't do it all in one go.
A good exercise to do at home is get a broom handle. they are about the right length for indoor use without taking everything off the windowcill and breaking the light fittings.
Sit on the floor in the middle of a spacious room. Or on the lawn - the neighbours thnk you're mad already, so don't worry about it.
With your arms comortably straight in front of you, about shoulder width apart. Keep your arms straight (not bar straight, comfortably straight that you can maintain when paddling). Now, just swing from side to side. keep the broom handle (your practise paddle) horizontal. You are just getting used to the body rotation part of the stroke as that does the most work.
Swing the broom handle from side to side, under control at a lazy paddling pace. Take it as far back as you can turn, this should be about 90 degrees (as if you were going to put the blade in right beside the stern of the kayak - in fact this is exactly how you should do that). then swing it round to the other side. Just swing it level from side to side like that 20 times.
Now, WITHOUT BENDING YOUR ARMS, do the same but dip the end of the broom handle down 45 degrees, as if you were putting the blade in the water - and do the same swing until your lower hand is level with your knee. Change sides - simply dip the other end and do the return swing. You will notice that by stopping where you did, the other is at the right place to start the next stroke comfortably.
THAT IS THE BASIS OF THE PADDLE STROKE. It is as simple as that. Your arms should only do about 10% of the paddle effort. the rest comes from your feet, calves, thighs, abdominals, lower back, upper back, shoulders and finally a bit from your arms. The lower hand and arm should be more or less just guiding the blade through the water and do no more than 5% of the stroke effort.
All this should be done with RELAXED HANDS, Your top hand, when paddling (not during the exercising) can be completely open. You do not need to hold the paddle at all, the water pressure on the blade keeps it pressed against your hand. Likewise, your bottom hand only needs to be a light crook of the fingers - you do not need to grip the paddle loom hard at all.
The benefit of paddling with relaxed hands is better blood flow, so you won't get cold hands in the winter because by opening and closing your fingers of your top hand (close it as it becomes the lower one, then open again as it pushes forward in the next top hand cycle). As you start the stroke with your lower hand, the two outer fingers first, remember....then like playing a clarinet, closing each hole in turn you go :-
pinky plus 3rd
pinky, 3rd, plus middle
pinky, 3rd, middle, plus index
stroke finished, change hands.
I have exaggerated it so you can understand what the feeling should be like. If you try too hard you will, in all probability, take the paddle blade too far back and create drag, actually slowing yourself down and doing more work for less gain.
Technique will outpaddle brute force every time.
Yes, you can rudder stroke with the paddle, but not at the same time as paddling! So a rudder allows you to maintain course and provide motive force. Remember, a rudder is NOT for steering, it is for staying straight. the rudder actually PREVENTS the kayak from turning!