It's funny that you come up with this as I was doing a quick search on this topic just 3 days before
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I read that many do it the way you make it. Further techniques used are:
- to make a mixture of oil and wax, which is like a cream
- to melt the wax and paint it on with a brush
- to soak the sling with wax and melt the excess out in the oven
I myself wasn't satisfied with rubbing it on and melting it in as the fibers I was working with were very soft and therefore I damaged the braid.
I personally wouldn't soak the sling as we want to protect the surface and not the inner parts. Further you need much more wax this way.
I came up with the following solution: I make very thin wax discs and coat the sling with it. Then I get a water boiler and heat up water. If you close the lid of it you have a single stream of hot vapour. Now you put the coated sling into the vapour and melt the wax discs on the sling. As the vapour provides the heat really fast the wax will also melt very fast. If you hold the sling diagonally while melting all the excess wax will flow away towards the "unmelted area" and only a very thin layer will stay on the sling. Any excess wax you can either just let drip of (and salvage it) or take away with a piece of kitchen paper or an old rug / piece of cloth.
The picture below shows the transition between melted and unmelted area. The wax discs are so thin that you can see through (and this is already more wax than we need).