Authentic Chicken Inasal

My son's birthday is coming very soon. I can't think of something to serve for our Pinoy friends aside from barbecue, so I looked online and found this recipe:

Ingredients:
2 Chickens (free range if available)
3/4 cup Filipino vinegar
1/4 cup Garlic finely minced
2 stalks Lemon grass optional
Salt
Annatto oil (see notes below)
Wooden skewers
Spiced vinegar

Additional Ingredients:

2 free-range chickens, approx. 3 pounds each, or if you can find smaller chickens, use 3 of them

3/4 cup Filipino vinegar, palm if you can find it, or cane; or if you must, the equivalent in kalamansi juice (available in the frozen aisle of your Asian market if you don’t have access to fresh)

1/4 cup garlic, minced very finely, or better yet, mashed into a paste with 2 teaspoons sea salt

achuete or annatto oil, made by steeping 1/4 cup annatto seeds in 1/2 cup hot oil for half an hour (If not available, you may mix a small amount of paprika and tumeric to achieve the same color.)

thick wooden skewers, soaked for 1 hour in water prior to cooking

Bottled spiced vinegar for serving, or make your own by mixing Filipino vinegar, lots of crushed garlic, a bit of salt, and a handful of Thai peppers or other tiny red hot peppers

Cooking Instructions:

1. Quarter the chickens, or if using the small ones, halve them. Marinate in the vinegar, garlic and salt, several hours or overnight, turning several times.

Preheat grill to 350 degrees. Make sure your grill is cleaned and oiled well. Cook over indirect heat for 20 minutes, basting with the achuete oil.

2. Turn and cook for 10-15 minutes more, or until thickest parts of chicken exude clear juices when pierced. Can also be made in a grill pan on the stove if no outside barbecue is available.

3. Serve immediately with the spiced vinegar. Other welcome additions to the vinegar: some soy sauce or fish sauce if you like, or even some minced ginger.Another technique we’ve found to work well, is to heat the oil in which the annatto is to be steeped, and to steep the garlic (and lemon grass if using) together with the seeds. This ensures a more even distribution of flavors. Just remember to discard this mixture when you’re done with the cooking, as you risk botulism from the garlic. Or, if you want to make it ahead of time, be sure to refrigerate the oil to retard any toxins from developing.

4. If your chicken is particularly fatty, you could render the fat slowly in a skillet, and use that instead of cooking oil to steep the annatto seeds. In which case, you’ll want to have enough not only for basting but also for serving later, as there’s nothing more appetizing than chicken inasal drizzled with this orange concoction.