Place salt, soy sauce, and 2 quarts of water in a large container. Stir until dissolved. Add the hens. If needed, add more water so the hens are completely submerged. Place in the refrigerator for 1 hour.
RUB:
While the chicken is brining, make the rub. In a small bowl combine the sugar, paprika, garlic powder, chili powder, pepper, and coriander. Set aside.
ASIAN BBQ SAUCE:
In a small bowl combine the barbecue sauce, soy sauce, sesame oil, and grated ginger. Chill until ready to use.
PREPARE THE HENS:
Remove the hens from the brine and rinse them under cold, running water. Place on a cutting board and pat dry. Using a pair of sharp kitchen shears cut through the bones on both sides of the backbone; discard backbone. Flatten the hen by lightly pressing on the ribs. Flip the hen over and tuck the wings behind the hen. Rub half of the dry rub over the hen. Repeat with the other hen.
GRILL THE HENS:
Turn all burners to HIGH, cover, and preheat for 15 minutes. Using a grill brush scrape the grill clean. Lightly dip a wad of paper towels in vegetable oil and use tongs to rub the grates with the oiled paper towel. Reduce all burners to MEDIUM.
Put the hens, skin-side down, onto the grill. Cover the grill and cook until the skin turns deep brown and it shows grill marks, about 12-16 minutes. Flip the hens, cover the grill, and continue to cook until the thickest part of the breast reaches 160-165 degrees F; about 12-16 minutes more.
Using a basting brush, brush half of the BBQ sauce over the hens that are facing up. Flip the hens and cook 3-4 minutes. Brush the rest of the BBQ sauce over the other half of the hens, flip and cook 3-4 more minutes.
Rest the hens on a cutting board for 15 minutes. Cut in half through the breastbone, then again at the thigh. Garnish with sesame seeds and green onions. Serve.