I haven't been able to think of query terms that cover this, so please pardon my ignorance.
30 YO ranch, basic rectangle. ~8" of cellulose insulation. I'm want to drill into a non-structural stud bay to drop a coax cable.
The top plate appears to be covered with 1/2" plywood

so I'm scared of missing the center line and drilling into the ceiling. Murphy is my earned middle name. I got two Greenlee extension sets to attack it from the bottom and promptly bound up the 3/4" auger bit so that was a no-go. Had to use a 10" 1/4" box end wrench to give me something to bang it loose. I tried drilling by hand with a ratchet, but the bit bound again.
So as always, TIA for any suggestions.
Dig around the cellulose and measure to drill from top?
Spade bit from bottom?
Cry?
Ron