When I started my MBA I was recommended
The Craft of Research as a good book to help me write better. I relied on it a lot. Later I started using
The So What Strategy which I refer to regularly as a consultant.
I also spent some time setting up my writing workflow. For me that was Markdown supported by Zotero (now Jurism) for references and Pandoc to generate a PDF for submission. But that workflow reflects my nerdy UNIX origin story and isn't suitable for everyone. My wife uses Google Docs with Zotero quite happily.