In a large saucepan, melt the jelly over medium heat; remove the pan from the heat.
Add the barbecue sauce, vinegar and hot sauce to the pan and whisk well to combine. Cover the pan and set it aside.
In a medium mixing bowl, combine the seasoning salt, Old Bay and poultry seasoning; whisk to combine.
Lay one layer of drumsticks in 2 full-size disposable aluminum steam pans, alternating the thin and thick end of every other piece so that they fit together nicely. Season the top side of the drumsticks liberally and evenly with the seasoning mixture. Flip all of the drumsticks over and repeat the seasoning. Add another layer of chicken to each pan and repeat the seasoning on both sides.
Cover the pans with foil and refrigerate 3-4 hours.
Preheat your grill at medium heat.
Arrange the chicken on your grill in the same way you did in the pans so they fit nicely.
Cook the drumsticks, turning them about every 10 minutes, until the internal temperature in the thickest part of the leg reaches 175º, approximately 1 hour.
To sauce the chicken, work in batches. Pour about 2 cups of the sauce in a very large mixing bowl, then add about 15 legs and gently toss/fold to coat them in sauce. Repeat the saucing with the remaining legs. Or you can put the sauce in a slow cooker and serve it beside the chicken drumsticks.
OPTIONAL: If you want to caramelize the sauce, return the chicken to the grill for a couple minutes per side after saucing.
If you need/want to grill the chicken ahead of time it will hold nicely for 1-2 hours in a 170-180º oven in pans covered with foil. You can even barbecue them the day before just wait to sauce them until just before serving or serve the sauce on the side. Cover and refrigerate the unsauced drumsticks overnight. To reheat, put chicken in covered pans in a 350º oven for about 2 hours, or until the internal temperature in the thickest part of the thighs is at least 165º