I know that Laur Duracoat is often dissed as not being as good as other finishes, but I have used it with good results. They do have a product for filling pits: DuraFil Surface Filler
This is one possibility for filing the pits.
I considered using it last winter on a Savage Little Scout boys .22 that had spent at least 50 yrs in a barn. Finally decided that the fun was in the relining and getting it working so I just blasted, phosphated and sprayed with Duracoat epoxy.