When ready to grill, preheat grill to medium.
Pour Italian dressing or marinade into 2 large dishes.
Place prepared shrimp, bacon, beef and chicken into one dish of Italian dressing. Soak and toss for 2 - 3 minutes to fully cover with dressing.
Place prepared pineapple red and green bell peppers and onions into the second dish of Italian dressing. Soak and toss for 2 - 3 minutes to fully cover with dressing.
Remove all from dressing and discard dressing.
Place shrimp in a grill pan or basket.
Place bacon, beef and chicken in a second grill pan or basket.
Place pineapple, bell peppers and onions in a third grill pan or basket.
Sprinkle all 3 with 1 portion of spice blend.
Place all grill pans or baskets on hot grill. Cook, constantly basting each garlic butter, while shaking and turning as needed until each basket is done cooking. Total time for meats and veggies should be about 10 - 12 minutes. Shrimp should cook much faster than the other 2. Cook until shrimp is just opaque - do not overcook - and remove from heat. (Alternately, if you are an accomplished griller, start the 2 grill pans or baskets with the meat and veggies first and add the shrimp at a time that will ensure all baskets finish at the same time.)
Place cooked fajitas on a serving plate or individual serving plates. For a restaurant-style serving, place on a cast iron skillet heated in the oven. Be VERY CAREFUL when handling the hot skillet.
Sprinkle lightly with remaining portion of spice mix.
Melt the remaining butter and serve tableside for drizzling.
Serve with warm tortillas for wrapping and sour cream, guacamole, salsa, shredded cheese and/or any other fajita addons you like.