WD40 is good for freeing off sticky cables, but the problem is it dont stick around long... see if your dads got some car engine oil in the shed, the thicker the better
would be better than nothing... but you just want a nice thickish lubricating oil, that dont just run all the way down and out the other end, leaving the cable dry...hence why i said thicker the better And the correct way is to disconnect one end of the cable and pour the oil down it... just lubricating the ends wont achieve anything!!
similar to what i normally do with cables, i dip the end then pull the cable through and back down then dip again and so on and so on