A couple of little tips on these adhesives use. First off you want the metal perfectly clean where the bonding will be. Running a nice new sharp 50 grit disc on the area is a must. We are talking only the areas on both pieces where they meet and the adhesive will be applied, be sure it is spotlessly cleaned with a NEW 50 grit disc, preferably a little 3" disc on an air angle grinder. It allows for much more control than a larger disc and tool.
If you have a large mating area like setting a hood scoop on top of a hood you will want to trail fit the scoop getting it on there perfect and marking all the way around at the edge. You could even mask off the hood around the scoop, you don't want the adhesive being anywhere but where the scoop meets the hood. The adhesive doesn't like to be pianted, or filler applied to it, you don't want it oozing out all over the hood. If you don't have large C clamps (24" Vicegrips are awesome tools to have) then you need to hold it down with screws until the adhesive cures. Heat is the arch nemesis of these adhesives so you can't weld up the holes if the glue is coming close to it. But if you remove the screws and fill it with a reinforced filler like "Everglass" that is as good as you can get using this method but there is still chance for "ghost lines" where those holes are.
Once the areas are cleaned like you apply a bead of the adhesive to BOTH surfaces. Then using an "acid brush" (anything will work to spread it out but they work so well) spread out the adhesive over the complete area where the two will be meeting. Brush it out over the entire mating area so there is no bare metal on both the hood and the scoop.
Set the scoop into place trying not to lift it up after the adhesive strips have made contact. If you have to move it a little slide it, but don't lift it, this creates air bubbles.
Clamp it into place with long C clamps or the screws until it sets as per manufacturers recommendations. Cleaning the adhesive out of the edge where it meets good after it's cured and applying an epoxy primer over it is as good as it gets.
If you plan on moulding the scoop into the hood, that is asking for trouble as the edge will likely show a ghost line after you are done and out on the road. But if you insist, applying something like Everglass (a very short strand fiberglass reinforced filler) over the seam making sure to leave a thin film over it, it can work remarkably well. But more likely than not you are going to end up with Ghost lines down the road.