For a block party, Buy two bottles of barbecue sauce - use 3/4 to marinate / pre-coat the meat for at least an hour (in the fridge) but leave 1/2 bottle to baste. Having a small cup and brush helps when basting.
You can separate the meat throughout if you’re the skittish type or planning on eating undercooked pork or chicken for some reason. Otherwise just throw it all in a bowl and shake it around with the barbecue sauce.
Tender pork and chicken on the barbecue require constant moisture. The radiant heat from hot glowing coals is superior to a windy gassy fire or large direct flames that create grill hotspots and tend to strip moisture out of the meat, making it tougher.
IMO it’s better to use (cheaper) cuts of these meats with a bit of fat to them, such as pork ribs, or chicken legs and thighs. Pork chops and chicken breasts contain more protein, making them more difficult to cook tender.
Avoid breaking skin or surface of meats with forks, etc. Use tongs for turning. At first, allow surface of small pieces (or edges of large pieces) to become semi - dried while the underside shows only the cooked color of the marinated meat (and grill marks).
Flip and baste, being careful not to touch any uncooked meat with basting brush.
Flip as soon as underside develops full color of cooked meat, then re-baste.
Continue to frequently flip and re-baste until meat is cooked to desired doneness, watching for “burn marks” between the “grill marks”. Seared meat and burnt sugar in the grill mark yield a very dark stripe when compared to the marinade. But “in-between” colors represent the results of different chemical reactions, many of which add to the taste. Flavors in the barbecue sauce will also be enhanced by the “browning” process.
If you’re the skittish type, a meat thermometer can reveal whether the meat is cooked to 175-180F, which is safe for both these meats. Otherwise, cook it 'til it’s “done”; checking by occasionally slicing through thickest part of a portion to check doneness.
BTW, Steaks are a different story.