Filling holes after panel bond

I built the lower rear quarter sections for my 70 and I installed them by flangeing the quarter and gluing with panel bond. I held the patch tight white a bunch of sheet metal screws.
Now how do i fill the holes? Can I mig weld them shut ? DO I need to use more panel bond,maybe using a piece of tape for a backer?
Panel bond and plastic fillers do not get along. You really need to keep it to a minimum. I’d glue the screws back in and grind them flush.