Hi Gal,
I've already used a batting 50/50 bamboo/cotton made by Pellon, the Legacy brand. It is very soft and cuddly.
As said on the lable the batting is not pre-shrunk and it can shrink - like cotton - 3-5%. It should be handled like a cotton batting and is completely washable.
For preshrinking the producer suggests to put it in the washer in warm water with no detergent, let it soak for 10 to 15 minutes and spin the water out on the lowest setting. It should not be agitated! It can be dried in the dryer on the low temperature for 10 to 15 minutes. Of course you can also air dry the batting.
I always use my battings without presoaking it, so what I wrote is what the producer indicates on the label. The batting hand quilts very easy and soft, drapes very nicely and I would compare it with a cotton batting.
Hope that helps!