I'm having some rooms redone in my 1860 foursquarish house. Pulled off interior wall and insulation to reinsulate to higher R value. The exterior sheathing is just horizontal planks with gaps between them and most are sealed with exterior tar paper and siding but I feel some drafts and I've seen a couple of actual holes to the outside. I know I need to address the holes, but for the mystery drafts, what should I do to effectively seal them. Spraying foam insulation is not in my budget.