I’ve also only ever heard it done on a wood axle. I also wax the area where loop on your finger rubs when looping, since that’s where my strings tend to break more. (I don’t know that it really helps, but it makes me feel better. lol)
All I did to do that is to put my string on a candle same as you’d put it on the axle, then give it a few turns, same with the finger loop.
Sheesh there is so much out of date info out there on this topic. I’ve used modern poly string extensively with my No Jive and Eh, both wood axles, and it does NOT melt.