I saw a YouTube video where a guy lets his dirty coils sit in rubbing alcohol over night, then another day in water, then gently rinse with hot water under the tap, then let dry another day on a heating vent. Apparently works well, but takes a few days. I have never tried it.
Learning to rebuild or stocking up on coils when on sale are the best options with building being the most cost effective by far.
That's an awful lot of faff to ultimately end up with a slightly cleaner spent coil. It would be SO much quicker to just build your own and change the wick. And don't forget, it will be a better vape too.
Cheaper, quicker and better when building your own. Why even consider cleaning factory coils IMO.