i use two layers of Warm and natural in my kids quilts, I made two twins this way. I like them heavy.
I had NO problem handstitching them. I mean, if it was a chore I would not have done the second one LOL.
If you got a good sharp needle, that makes all the difference. For me stitching through mutliple seams is hard, but all in all stitching through batting never gave me any trouble. You can always test it out first. Make a small sandwich and see how it goes.