"Crusty" Swish curtain rails

Primrose

Over time our white plastic Swish curtain rails have become rather pock-marked and a little like sandpaper, so it's now quite difficult to open & close the curtains without the hooks on the rail dragging & catching.
.
Is there anything I can do to "smooth" the rails? I've tried thoroughly washing & drying with soapy water, but that hasn't worked so I need to try something more drastic as I don't want the hassle of having to take down the curtains & replace the rails.

Gloomendoom

Try rubbing them with a candle.

Avoriaz

Silicone furniture polish might help.

Mr Sheen worked on ours when we had them, although they were not pock marked.

esmy

Just spray with furniture polish - don't wipe it off .

Biggles

WD40 works well.

Primrose

I've just tried spraying & wiping the rails with aerosol furniture polish and they are now opening and closing much more smoothly. Many thanks !