I like to use straightened pieces of coat hanger wire with a sharply-angled cut on the end as "feeler" drill bits. They are great for finding your place in a wall from the attic or even below. If you are in a bad spot, you can adjust your position and the hole is barely visible. I also keep a small tube of toothpaste for patching these holes in the ceiling or when I scratch a wall.
I do the same with seismic wire, always keep a few on the truck. I drill thru wood floors behind the base board, a tiny dab of caulk afterwords and nobody can tell I was there.
