I use mayo every time. Mayo is just egg and oil, a poor man's aioli. It helps mine with keeping the rub in place and the skin golden. YMMV. That being said the last two birds I did for a bbq class last weekend I rubbed with Simply Marvelous Season All, Sweet Seduction and Pecan. Another I added Big Dick's Dry Rub to it, both with outstanding results. I spatchcocked one and the the other whole to demonstrate time and temps for finished product. Here's a cross section of the spatched breast.