This is one of the biggest challenges I have had, so I'm still learning the best result I have had...
Whole chicken. Spatchcock chicken, dry with paper towel, Give an extremely lite dusting with baking powder and place in the refrigerator. This I think dried out the skin to allow to crisp up. Once bringing the chicken close to desired temp I opened the grate to sear the skin until chicken done.
If you have a horizontal smoker/pellet grill it might be easier to crank it and crisp it later on, but if you have a vertical, it might be tough. I am resigned to the best I can hope for is doin bite through skin instead of crisp.
I've had pretty good success by bringing my smoker to high, putting the chicken on, skin side down till browned up. 10-15 minutes maybe. Then removing the chicken, get the grill down to smoking temp, put chicken back on and smoking to 165 degrees.