For the Chicken and Sandwiches:
Combine the sauce ingredients in a pot and bring to a simmer. Let simmer for about 15 minutes and then cool.
Season the chicken with salt and pepper and place in one or two large plastic food storage bag with half of the cooled sauce. Let marinate for anywhere from 3-24 hours.
When the chicken is marinated, preheat a grill to medium high and cook, turning every now and then for about 30 minutes or until the internal temperature of the chicken reaches 155 F. Cover and let stand about 10-15 minutes as it carries over to 165 F.
To create the Huli Huli Sandwiches, chop the chicken meat, discarding skin and bones, and toss with the remaining sauce. Pile some lettuce on the Hawaiian bun bottoms, top with saucy chicken and pineapple salsa.
For the Oil-and-Vinegar Slaw:
In a mixing bowl, combine the coleslaw mix and red onion. Add the vinegar, oil, celery seed and a pinch of sugar or honey. Season with salt and pepper and toss to coat. Refrigerate until needed.