[Closed] Tricks for getting a Reverb Sheath to route through a frame

I have a new Reverb Seatpost and any easy trick to routing it through the frame. Its a Ibis HD3 and the cable ports near the BB are seized up due to man sweat, so was trying to get the hose in via the seat tube. I managed to tread the hose most of the way, but It got hung up in the top tube against the internally routed cables.

Someone must have come up with an easier way to deal with this (apart from no seat dropper and externally routed hose!).

I was thinking some string with a nail on the end of it and a magnet on the outside of the frame to guide it. Any other suggestions?