I have owned several Gew 98s like this, or smell musky from being stored an attic or a horse barn. I think your truly better off just taking it apart and letting it sit in the air. I agree with putting it in a closet, cardboard attracts moisture depending on how humid the area is. My 1918 Amberg smelled musky for months but its tolerable now, I just let it air out. Don't use BLO. Modern BLO is chemically different from what was used during that era. I'm not an expert on K98s, but I promise you the stock finish changed drastically during the war. For example, during WWI they switched from Linseed oil to train oil in 1916. Trust me, you can pick out a K98/Gew 98 instantly that's had the old BLO treatment.