First, I chamfer the top of the hole(s) back to bare metal with an angle grinder (just to make them a little low, and I'll feather out the surrounding area). I take an old drum of reducer, and cut the bottom out with tin snips, which I'll then cut into appropriate sized strips to cover the hole with about 0.75" overlap over the hole. I rough it with 80grit, and rough the backside of the panel too. I then use Lord Fusor 108B metal bondline adhesive which glues the two pieces together at weld strength. Let it cure, follow up with Kitten Hair filler, sand back, then finish with either U-Pol Fantastic, or Dolphin finish filler. Highfill and your done......ready for top coat.
No sink back, bullseyes etc.