Ask HN: How can I teach back end contracted team front end development?

I've been tasked at work with training backend developers to be capable of writing high quality frontend code in react and redux (high quality as in maintainable, consistent patterns, follows ux designs). I've really struggled with this. The external team has produced low quality code quickly that required rewrites and long cycles in PR review.

I've tried implementing mentoring and pair programming but that seems to stick for particular use cases / features but there is a gap in general knowledge shown by repeating the same mistakes on future features.

I feel like there is a massive difference between accomplishing a feature vs being good at something.

Any advice or feedback would be really helpful, thanks.