I think half chickens can be grilled any number of ways and still come out great. Putting then in a brine of salt water, diced onions, juniper berries or pickling spices would work. But only brine for a couple of hours. A good old red BBQ rub is always great. Mopped with apple cider (or sprayed), or lemon juice, or beer and spices is always good. The trick is not to dry out the breast meat so make sure you have at least a two level fire so you can move the chicken to a cooler spot. Steven’s “How to Grill” has some good tips for grilling half chickens.