How do I use existing recessed cable plates to hide AV cable

This seems to take a fishing system to extremes. Maybe call in the electrician and let them fish or pull it for you.
Bob

It would seem the plate is there for a reason. If so, and you and you can find both ends of old wires, you use one sturdy piece as a pull wire. In other words, you pull a new wire with an old one. When you do that, it's smart to also attach a pull string at the leading edge of the new wire and leave it in the wall for possible later use.

First of all don't do it with the plates on the wall, take it off first. Now use an "electrical fishing tape" to get it done. Good luck.

Perhaps the easiest is as the previous post, tie and tape (at least 12") a pull cord to an existing wire and pull it back. Then tie the pull cord to both the new and previous cable and pull it back through.

A fairly new and simple to use fishing pole for electricians and cable installers uses two super moly magnets. One is attached to a fiberglass rod and the other is attached to a pull cord and fed by another fiberglass rod from the other end. The magnets attach together and takes nearly 10 lbs to pull them evenly apart which is usually enough to get a pull cord trough the wall.

All in all it still usually takes two. One to feed the cable and one to pull. It can be done by one if you lay the line right.