I use a paint stripper heat gun about 10cm distance and keep it moving along and around the cable. I stop when the cable feels very hot to the touch, but obviously not burning my skin.
A telltale that you may be overheating is if the outer shield on the cable goes from dull to shiny.
Make sure you let the cable cool to near ambient or less before cutting the zip ties and removing from the dowel. I'm impatient so I put it in the freezer for a few minutes.
My heat gun is like this:
https://www.bunnings.com.au/xu1-2000w-heat-gun_p6290580