RE: using blind nuts/securing cowl
You got a lot of good advice already. But if you want to do the blind nut way. I have put a wire through the hole and fed it through to where I had access. Then slipped the blind nut on and put a loop in the end of the wire. then pulled the wire back the other way till the blind nut started. Cut the wire and quickly started a screw in the blind nut so it could be seated. Then shook the plane to get the wire end out. It's not a perfect way, but it will work. This is assuming there is an opening to get access to the wire.
David