There seems to be no specific answer as to cover or not during the dry brining process. 

 I have always covered my pork shoulders & had good results. 

 From what I conclude, brining uncovered has the potential of drying out the surface, or producing a more crispy skin.

 What say you? 

Your post interests me because I will dry brine this year's turkey and decided to not cover it.  I've always wet brined my fowl.  This is an attempt at crisper skin.