Remove heads, feet, giblets and excess fat from ducks. Using poultry shears or strong kitchen scissors, remove tails and backbones; cut each bird in half through breastbone, then in quarters. Rinse and pat dry.
Prick all over with the tines of a fork. Combine herbs with salt and pepper and rub all over duck pieces, pressing well into skin.
Place quarters on a rack in a roasting pan, skin side up, and cook in a 300 oven for about 1 hour, until the fat has rendered into the pan - up to 2 or 3 cups.
Remove from oven but leave on rack to continue dripping for about 45 minutes.
Start a charcoal fire (a covered grill is most efficient for this) and when coals are ready and spread, place duck quarters on rack, skin side down.
Cover grill and cook 10 minutes. Turn duck, cover grill and cook 15 minutes.
Reverse and cook skin side up for about 5 minutes more, covered; serve immediately.