Prepping the wrists for handstands should not only involve static stretching. The key is to strengthen the wrist through an extreme range of motion (eventually and safely). This is also especially important for those looking to tackle the planche.
In the video you will notice some basic movements that are easy to implement that require no equipment. I should also mention that wrist levering (see Chapter 8, Accessory and Grip Work) in a wide variety of ways will also have a fantastic benefit.
Starting from quadruped, rock back and forth and make shoulder rotations with a variety of hand positions.
From there, press through the hand up and down into that deep stretched position for reps.
Eventually move up to the fingertips and repeat the movement, you are using the ground as a fulcrum for putting force into the ROM.
Do the same movements on the back of the hands in a variety of positions.
You may feel some residual stiffness at first so rather than be super aggressive with the load, do lots of easy repetitions to let it open up more gradually and you will notice a big difference.
At the end there is some easy nerve flossing wrist figure 8's that combine the median, radial, and musculocutaneous nerve glides which I find an awesome bang-for-your-buck.
There are a LOT of other things you can do to prep the wrists but I would consider these to be the bare bones of wrist prep.
Any questions just let me know!