Hi Gene,
My collection now is basically, blades but at one time I had many guns. To repair/fill breaks etc I kept a supply of broken stock pieces and used suitable wood and colour to fill breaks. A useful way to "match" the colours is to use CONDYS (???spelling) CRYSTALS. Mix a VERY small amount of the crystals with water, which is all you will need. It drys brown and when dry, bone it with either a piece of smooth bone or even the round shank of a screwdriver. Amazing what it will hide in terms of new repairs. For broken horn or later plastic butt plates I used Epiglass Plastic Steel. Its black and when sanded and polished it does a great job.
With your current weather patterns be careful not to get wool fibres from your gloves mixed up with your repairs.