I ran ethernet from our basement to a couple of bedrooms by passing the lines through where plumbing goes to the attic for the soil pipe vent.
Finding inside of wall from attic.
Use interior walls only.
It will be next to impossible to drill downward under the portion of the roof that slopes to the attic floor without a right angle drill.
When working from an attic space it will be significantly easier to access a wall space on the floor below by working either an interior wall or the exterior wall that is on the gable end of the structure.
All holes around the edge of the attic need sealing with mesh wire screwed with screws to prevent mice from coming back.
Clean the attic first and remove any mice droppings and nests that you can find.
There are usually two openings far apart.
How to get rid of mice in attic with blown insulation is a little different than a regular attic because of the insulation.
For the mouse baiting in the attic and the basement should do the trick along with finding and securing the outside opening to ensure more won t find their way in.
Besides wall damage you may be able to hear dripping coming from inside the wall.
After all without a method to your madness you d just be hammering unsightly holes through your drywall in a vain attempt to cross paths with your wires.
If you need to find the wires inside your walls you ll probably want a non invasive way to look for them.