Is there anyway currently to upgrade the finishes (Worn/Scarred/Standard/Refine/Pristine) of a weapon card ?
No, there’s no way of polishing cards to a better finish and such a thing won’t be added at this point.
Previously, according to this https://www.dirtybomb.com/news/faq-weapon-skins/ there was a trade-up system.
We’ll be introducing a ‘Trade Up’ system next year
It never happened.