I gave up trying to get crispy skin on my WSM 22. I just can't get it hot enough. I can't get more than about 280 for any length of time, unless I crack the lid, at which point the temp zooms up out of control quickly.
But if you're able to hold temps around 400, you should be able to get the skin crispy. I cook chicken on the gasser at 400 - 450, and the skin comes out as crispy as a pork rind.
I almost never cook chicken whole. In fact, I rarely even bother with breasts at all. Breasts have to come off at 160-165 IT, which means they aren't on long enough to get the skin really crispy. Thighs, on the other hand, need to be cooked to 180 - 190, which allows more time to crisp the skin.