I packed my interior (back when it had one) with a bunch of 8 unit of silica gel desiccant bags on the back floor and in the trunk, but that was cause my company made them and I could get them for free. I put a humidity meter on the dash and it never got above 15%. Really kept the mildew-musty smell down. I kept them in there all year round with the windows rolled up and the vents closed. Kept it dry even during the dampest summer days. Folks use them in RV's alot. Another good way is to buy the desiccant in bulk and put it in open metal paint cans. In the spring, you can take the gel and regenerate it in the oven. You can do this pretty much forever.