I made a userscript to make getting the skin add command easier from the steam workshop webpages. It's new and probably buggy. Let me know if anyone has any issuues and I'll fix it as soon as I can. (You can report bugs on the site but please not here.)
FYI: It is only known to work with the TamperMonkey Firefox and Chrome extention.
https://greasyfork.org/en/scripts/404138-rust-workshop-skin-id-collector