Fiberglass Insulation to stop air infiltration?

I recently discovered the kitchen addition to our house (probably put on in the 50's) has no 2x4 headers in the walls. Don't ask me how they did this but you can literally reach down into the walls from the roof crawl space over it. So... since the roof soffit(?) is vented any breeze was going all thru the walls and down wire chase into basement etc.
OK so I get my teenage son up in the hole I cut in the ceiling and we started tightly rolling up pieces of faced fiberglass insulation and stuffing them into the top of the wall cavity.
My questions are...Will tightly packed/rolled fiberglass insulation stop air from going down walls? Also there were two wall spaces with wires (looked like first generation of romex) where we just loosely filled in some insulation, is this going to get soggy, something about dewpoint I read somewhere? Should I take out and pack loose insulation in plastic bags an re-install? I don't want moisture by wires but I really want to fix that damn breeze in the basement. Any comments would be welcome as I don't want to have to go back in once I re-sheetrock hole in ceiling.
PS. Not only was lack of header leaving nothing but (early) wallboard between me and the outside, when they cut/added on for the roof over the addition they tore off siding and felt paper leaving those nice 1/2 inch gaps between diagonal planks! I can see the bottom of my freakin bathtub! (floor joists run perpendicular to that side of house) No wonder house always felt drafty!!!!
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Blown in insulation will seal a lot better.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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