I have had success with Middleburn Cable Oilers (google, of course). They are a little widget that fits in the middle of a length of cable outer. They have a hole the size of an aerosol straw. I use them on the pre-rear-derailleur cable loop on my mountain bikes - these last loops of cable get full of mud and seize up a lot. The benefit I get from the Cable Oiler is that I can use a can of aerosol (I use silicon lube fwiw) to blast out the mud. So - perhaps more a cleaning aid than a lubricator. hth