About 2h strokes 
How to link the left hand to the racquet.
http://www.youtube.com/watch?v=iTHO5-JnARM(Turn on the subtitles)
Well, the animators who have already made a 2h backhand know the problem with the left hand because we have to modify it frame by frame to have a descent looking anmation. And sometimes it's not enough because the hand's position is not precise enough. I don't know if it has been posted yet, but here's a solution.
1. Be at frame 0
2. Click on the biped's left hand
3. Go to the "Motion" (#4) panel in the right bar
4. Go to the "Key Info" tab and expand it
5. Expand the "+IK" submenu which will then become "-IK"
6. Click on the right-up white arrow next to the rectangle
7. Click on the grey racquet shape aka the "bone_rocket" object
8. Select "object" just above the rectangle where should now be written "Bone_rocket"
9. Increase "IK Blend" (still inside the "-IK" submenu) to 1.0
Now, the left hand will stick to the racquet wherever it goes. If it goes to far, it will still follow it but won't be able to "grab" it unless you make it come closer, then it will return to the position where it was touching before the reach was too far.
The hand starting position isn't important because you can still adjust the left arm / left hand when it's position becomes awkward.
About gestures 
How to link the racquet to the hand you want and changing it whenever you want during your animation
http://www.youtube.com/watch?v=lkpeMoa-T3k(Turn on the subtitles)
When I first made Nadal's vamos or the racquet throw, I used to modify the racquet frame by frame which was extremely annoying. It is, above all when it's linked to the right hand (and moves along it) and you have to make it move following the left hand.
This era of horror is over.
You can easily link the racquet to differents objects through the animation.
1. Click on the racquet
2. Select a particular frame
3. Go to the "motion" panel
4. Go to the "Link params" submenu
5. Click on "add link" then click on the object you want thte racquet to be linked to (head, foot, hand, whatever you want)
6. Then animate the object so the racquet can follow

7. You can link the racquet back to the right hand if wanted, just do the same at another frame
8. You can delete the links created easily by selecting the link in the dialog box then clicking on "delete link"
