Prep-Ahead Tip: Split, flatten, rub, and refrigerate the chickens a day or two in advance of the party (or pop them in a cooler if heading off on a different outdoor adventure). The longer they marinate in the dry rub, the better the flavor, and it makes for easy grilling when it's time for the backyard bash to start. Prep-Ahead Tip: Make chimichurri one day ahead and press plastic wrap on surface, to