Freeze the tri-tip for 45 minutes. Remove it from the freezer. Slice the meat into slices the thickness of bacon.
Place the meat in a bowl and season with salt, pepper, Creole seasoning, garlic and onion powder.
Heat the grill to around 400F degrees with an indirect cooking area and hickory wood chunks.
Heat the oil in a large pot on top of the grill. Add the onions. Sauté until tender, stirring occasionally.
Add the beef and stir to combine. Close the grill lid. Let the meat cook, without stirring, for 10 minutes.
Remove the pan from the grill, and close the lid to maintain the proper temperature. Using two metal spatulas, tear the meat apart to shred. Hold one portion of the meat down with one utensil and pull the meat apart with the other utensil. Continue with this process, until the meat is in bite-sized pieces.
Place the skillet back on the grill, and add the broth to the pan. Close the grill lid and heat for 2 minutes. Stir in the mayo to combine.
Add the American cheese and stir, until melted. Add the Provolone cheese and stir until melted.
Slice the hoagie rolls into 2-inch squares and arrange on a large platter. Serve the dip warm with slices of soft hoagie rolls.