Regarding the remaining questions: IMO, if the other writers want the crash course, they're going to need a lot of resources they may not have on hand. Namely money.

Crash course? Private tutoring for the written language, especially in fiction writing (more on this bit later). Immersive language learning.

The fiction writing thing will be the most labour intensive for tutor and student: Student attempts a short descriptive paragraph, tutor breaks it down and explains *why* something is wrong and what the correct version should like. Then the student goes away and practices till the next tutorial session. Rinse repeat with all aspects of fiction writing / whichever type of writing the student is pursuing. Oh, and immersive reading.

IME, it's not a case of pushing aside your native language; it's more learning how to be comfortable code switching.