I like Loctite - 0151 Hysol epoxy for foil repairs. It’s thixotropic and has a light paste texture so it will sit exactly where you put it in the shape you put it in.
It dries clear.
- Sand out and clean the damaged area to remove any loose material
- Put clear packing tape around the damage
- Carefully fill in the missing material with epoxy, popsicle sticks work well to shape the repair and remove excess
- After curing, remove packing tape and assess the amount of material which needs to be removed to blend. If there is any significant amount, tape around the repair with blue painters tape and slowly, patiently sand away the excess. Be careful not to sand the non-repair area until the excess is fully removed and only then with 600+ grit to blend the repair in.
I buy the packs of sandpaper that go from 120 to 2000 grit along with a variety of foam sanding blocks with coarse grit.