To de-rust rusty writing muscles is same as moving actual muscles.
Just start writing/moving. Find every opportunity to exercise those muscles.
The aim is to establish a new habit in your lifestyle. Keep it light and easy.
If thing start to get stale, switch things up.
After 10k words in 5 weeks, I'm up-ing the difficulty
By also writing a weekly newsletter the Specific
Issue 2 talks about the best feedback i got for my writing.
Check it out this Saturday
https://simkimsia.substack.com/