I'd start by getting into your flybridge and start tracing where stuff goes now.
A tone probe is also fantastic following wires. Put the tone sender on one end of a wire and the probe will help you follow where the wire goes.
https://www.amazon.com/Greenlee-601K-G-Basic-Tone-Probe/dp/B0042VII5W
Sometimes getting from point A to point B takes a more circuitous route than you'd expect. The flybridge on my boat runs a TON of stuff down from the lower helm, forward to the A-pillar of the windshield and then inside that up to the flybridge. And there's an oddball access panel in the ceiling of the starboard stateroom that provides access to the base of the A-pillar. I wouldn't have assumed this (as the B-pillar is MUCH closer) but following the probe signal told me otherwise.
That and in addition to the fiberglass poles (which are great) it's helpful to have a flat fish tape. Not the typical wire type. I find the flat kind seems to slide better along/through various spots without getting stuck. The thicker wire kind are good in some situations but I've often had trouble with them getting hung up.
https://www.amazon.com/Greenlee-438-2X-Steel-Fish-Tape/dp/B001HWEEIY
There are now some really inexpensive borescope cameras on the market now. I've got one that's wireless. You connect your phone to it's wireless signal to see the live signal. This is an improvement over the kind that plug into your phone, as those tended to be a hassle trying to juggle both the camera and the phone ends. This wireless one lets you rest the phone in your line of vision while keeping your hands free to move the camera.
https://www.amazon.com/gp/product/B07DNNSM1L
What I haven't yet found is a good, BRIGHT, light on a gooseneck. I've got a magnetic base one that's proven handy, but there's nothing magnetic the boat for the base to grab. Still, the 20" gooseneck has proved useful for twisting the light into tight places under the helm and inside columns.
https://www.amazon.com/gp/product/B07L6T1N1K
I've also found it's sometimes helpful to do the work in either BRIGHT sunlight or after dark. Sunlight shines through thinner places in the fiberglass, likewise a BRIGHT light if it's dark. Which can be helpful finding just where there is or isn't a way to get things through somewhere.