[embee]

I like to use Halfords "Nylon&Rubber lubricant" for cables, comes in aerosol. I think it's now called "Silicone lubricant for rubber and plastics", same stuff.

Ideally disconnect the cable at the top end. Make a small funnel arrangement from tin-foil or similar at the cable outer, hold with a rubber band, then squirt some lube in and work it up/down. Many cable sare nylon lined these days, and it seems to suit the application well in my experience.