Set out plastic wrap.
Remove the membrane from the back of the ribs by slipping a knife between the membrane and bone of one of the ribs until it starts to separate and you can get a good grip on it with your hand and pull the membrane off. It should come off easily. Repeat for all racks of ribs
In a small bowl combine the mustard and pineapple juice and mix well. Brush on both sides of all three racks of ribs. Place on a tray, meat side up so the marinade doesn't smear off on the tray and marinade for one hour in the refrigerator.
In another small bowl combine the spice rub. Set out a long piece of plastic wrap. Sprinkle a tablespoon or so of the spice rub on the underneath side of one of the racks of ribs and place the rack of ribs on the piece of plastic wrap, sprinkle another few tablespoons, 2-3, of the rub on the top/meat side of the ribs then wrap in plastic wrap gently pressing it against both sides of the ribs. Repeat with remaining racks of ribs, reserving 2-3 tablespoons of rub mixture.
Refrigerate the plastic wrapped ribs on a tray at least 6 hours up to 24 hours.
When ready to bake the ribs, remove them from the oven and let come to cool room temperature about 35-45 minutes. Preheat oven to 250 Deg F.
Line a large baking tray with foil and place baking racks on top. Remove the plastic wrap from the ribs one rack at a time and wrap in foil, sprinkling a tablespoon of the reserved spice rub mixture over the top before completely wrapping in foil.
Place in a center rack in oven, ribs can be next to each other on one tray or if they are too big you can place them on separate trays on separate racks of the oven. Bake for 3 hours, switching trays if using two racks of the oven at the halfway point.
Remove the foil and bake for another hour or until you reach 180 internal temperature or a bone gives way easily when pressed.
Slather the tops of the racks of ribs generously with bbq sauce then broil, about 6” away from the heat source for 3-5 minutes until bubbling and starting to char a little. Keep a close eye on the ribs so they don't burn when broiling.
Rest ribs for 5 minutes before serving. Serve with more sauce, Hawaiian BBQ potato chips, slaw or salad, pineapple slices and of course Hawaiian beer. Kona Brewing Co Fire Rock Pale ale is one of my favorite beers to drink when eating ribs.