It is always a pleasure to discuss spin bowling. I might veer off at a tangent at some points here.
1) There are a few different ways of releasing the ball with the fingers, I do not really use my fingers to generate spin, they just transfer the torque I generate from supinating my arm (not sure if you are familiar with the terminology, basically supinating is rotating outwards like a finger spinner, pronating is rotating inwards like a wrist spinner).
Almost all spin is initially generated from the position and rotation of the arm in the action. I am aware of some deliveries such as a carrom ball that a finger flicked, but in general I think the fingers transfer the spin, rather than generate it themselves. The movement of the wrist - flexion or extension - also acts as a torque magnifier. Bowlers like Warne and Murali extended their wrist to generate their prodigious turn, but many bowlers do not use their wrist at all.
2) My only solution was to practice ensuring a clean "release" with the fingers, in which all the torque is transfered down the front or the side of the ball rather than down the back. We all know what it feels like when the ball doesn't quite come out right because the wrong bit of finger has brushed on it. I tend to grip the ball with my index finger slightly bent so that the tip is pressed against the seam to ensure that this is always the last thing to touch the ball as I let go of it.
Secondly, focus on really trying to reach round the front of the ball and bowl with as much topspin as possible.
3) If you think of a raised arm with the palm facing the batsman as the "neutral position", you can then rotate it in either direction so the back of the hand is facing the batsman.
My opinion is that for the majority of people, it is biomechanically harder to bowl a delivery with a fully supinated arm (ie back of the hand facing the batsman like Murali) than it is for a fully pronated arm (back of the hand facing the batsman like Warne). This is purely to do with the movement in the shoulders etc.
3) Leading on from this, we can discuss offspinners and legspinners actions as points on a continuum where the two extremes with significantly advanced or retarded hip rotation compared to completion of the bowling action. A neutral action (eg Swann) is about in the middle, where the hips rotate in time with the bowling arm coming over. An "extreme" offspinner's action such as Ajmal's see the hips rotate ahead of the bowling arm, this allows a greater deal of supination at the point of release. An extreme legspinner's action looks a bit like bowling off the wrong foot and allows extra pronation. This is quite common amongst bowlers who specialised in googlies. Mushtaq Ahmed was an example of this.
To copy an extreme offbreak action, simply delay your bowling arm coming over a little later until the hips have rotated that little bit more than usual and try to extend your wrist towards the batsman with your palm facing back towards your face. Look how Murali has rotated his hips right round so his chest is facing midwicket - and he hasn't even released the ball yet.
Hi SLA – thank you for the advice – it was nice to get comments from someone who has already spent time working out what is required to get more top-spin on the finger-spin delivery.
Today I tried carrying out your advice in order to bowl deliveries with more top-spin. I managed quite quickly to achieve a more-regular 45 degree delivery and once managed a 5 degree delivery (near pure top-spin)! The key to what you described is bringing the bowling arm over later than usual.
I used the following five steps:
(1) front-arm goes up as normal.
(2) Back hip drives through (get up and over the front foot).
(3) Then the bowling arm goes over (with high arm action).
From doing these first 3 steps I found that the top half of my body swung around finishing a much more open-chested position than normal before releasing the ball.
(4.) Turn the wrist turned around as far as possible (in order to get top-spin). If I try the alternative Mulari style release the ball sometimes gets “chucked” out.
(5.) Bowl with the intention of putting the ball in the air. (Imaginary curtain/net to bowl over in the middle of the pitch!)
I will keep working on this and find out what works best!