WHY do you let the bird dry in fridge after brining?

I am by NO means a master at this but from what I've gleaned so far is that partially the reason for allowing the turkey to dry is that unless you have a consistently mean hot smoker, the skin will not crisp up. I also know that you generally would want whatever you're smoking to be dry as the moisture would prohibit the smoke from adequately reaching all the meat. Secondly, I can also attest that when smoking salmon, which I have done quite a bit, part of the process is after rinsing the fillets you WANT them to air-dry until what's called "pellicle" is formed. It would be like what the surface of a basketball looks like. It helps more smoke adhere to the meat, so I'm guessing the same principle applies to when you want your turkey reasonably dry as opposed to dripping wet. 

Hope this helps and Happy Thanksgiving to you and yours!

If you're going to cook at lower temps air-drying the chicken for several hours in the refrigerator increases the odds of crisping the skin. It's not a guarantee but it can help.  If you go at higher temps I don't think it's required. 

Tender loins, It is difficult to get Crispy Skin at temps under 300*F and Impossible with wet skin. Your idea of smoking, then going on the Grill is a good one, however if there was Sugar in your Brine the skin can Burn in a NY Minute. Considering all a less risky choice is to Smoke to an IT of 150*F and go in a 425*F oven to crisp the skin and get to a finished IT of 165*F...JJ