I done this myself a few months ago. It is a bit fiddly and as you say you can't actually see where you've got to go.
It was my intention to do a 'how to' so I took lots of pics, but haven't got round to writing one yet.

For the part your talking about I found it it best to do it in two stages-

First I used a large cable tie and went from the gromet in the boot to the top of the bumper (see below)





Then I used a rod behind the bumper to the number plate light-hole (see below)



Join the two together



And pull through






Hope that helps.

As said I'll try and do a 'how to' soon.

 

Many thanks to @SamMcGoo for your advice, using a method similar to yours (a length of TV coax cable) camera is all installed and wired in the at the rear.

But... Having disassembled the instrument panel and got to the back of LCD, I was expecting to find an RCA\phono connector to plug into, but alas no.

Do I need some sort of loom adaptor, or breakout connector to convert the RCA plug into something more useful?

 

How did you get on with this? Looking to get one as well but did you need an extra connector?