Trek Domane

[Peat]

Further to my internal routing moan - Not a Domane specific tip, but for all IR bikes.

Jagwire do cable liners (Slick Lube Liners) that I think are mean to act as an addition barrier to the cable within the outer. Anyway, some of these cut to the lengths (+ a bit extra each end) of your internal route legs mean you can slide them onto the existing cable then withdraw it leaving the liner in place. Then it's dead easy to thread a new one back down these liners.   

[Giropaul]

I’ve bought lengths of liner for re- cabling, 10 metre or so lengths. I think I remember that it came from Taiwan or somewhere ( so may be less available and more expensive post- Brexit)
Jag wire also do some very low friction cables for the complex cable runs through bars, extensions etc and totally hidden (aero apparently).