There is a device available that clamps to the end of a cable & allows cable lube to be injected throughout the entire length of the cable.
I can't remember the name, but I found mine at a motorcycle dealer a few years ago. They work good, just have a rag at the other end, cause the gunk that gets forced out can cause a bit of a mess.

Larry W - 99 VX s/c
3" lift w/trimming & BFH mods, rollin' on 33/12.50x20" Nitto Mud Graps. Indy 4x h-d tie rods, lower links & a bunch of other stuff that put the hurt on the wallet.