On Saturday, December 7, 2019 at 6:12:08 PM UTC-5, soaringjac wrote:
Any recommendations on what to use to fill small holes in an aluminum panel?

Very small(screw) holes can be filled by counter sinking and putting a flat head screw in, followed by a bit of filler.
Larger(switch size) holes, assuming no interference with something on the back face, can be covered from the back by a small piece of aluminum, bonded with epoxy, followed by filling he hole with body filler.
Unsupported body filler will fail in a short time.
Good Luck
UH