First prepare your marinade. In a mixing bowl put all the marinade ingredients and mix thoroughly. Stir well to blend and combine all the flavours of the spices and seasonings into one wonderful marinade.
Taste and adjust the seasonings and acidity level. Different vinegar provides different levels of acidity, so final adjustment is necessary. At this point you might also want to soak your bamboo skewers in water.
In a large bowl or casserole, place all the drained chicken drumsticks and wings. Check the timing of marinating and start of grilling. Allow at least 45 minutes of marinating before grilling the meat. At any rate, do not marinate more 1½ hours. When you have synchronized the timing, pour the marinade and stir to evenly coat the chicken pieces. Stir every 15 minutes to ensure even infusion of the flavours.
While marinating, prepare the basting sauce. In a small pan heat the vegetable oil until hot. Drop the annatto seeds and steep. Take as much colour and flavour as possible. Remove from heat and carefully discard the seeds. Into the resulting annatto oil blend the margarine and let it melt in the residual heat. Add the ground pepper, stir once more and set aside. Don't skimp on this.
After 45 minutes to an hour, take your bamboo skewers which have been soaked in water and skewer the chicken pieces one by one. You can fasten one drumstick followed by one wing in a single skewer for better presentation. Your charcoal grill should be ready by now.
Cook the inasal in batches on low flame. Baste the chicken several times while cooking. Be careful not to overcook. You should cook the meat but must maintain the moist inside. Inasal is better with slightly, just slightly, burnt skin. It adds smoky flavour to the meat.
Continue grilling until all the chicken pieces are done to perfection. Ok, that's hard to do as some will surely get scorched as you will be busy tasting the first batch of inasal over a bottle of beer. It's still alright. It's part of the grilling process.