NigG,
'Dry polishing' one's webbing was simply a means of ensuring that its finish was a little more enduring.
After one had done the Blanco job, a clean boot-polish type brush was used to bring a smooth effect which didn't show wear marks - for a couple of days, at least.
It looked good and was very practical - but no, it wasn't what the foundations of the British Empire was built upon.
One had to go stand in the naughty corner when found out.