Organization!!
I set aside a chunk of time within my first month to update my interview forms, create Excel spreadsheets (patient info, checkboxes for whether I submitted my report, was waiting for feedback, when I uploaded it into Epic, who & when reports were routed, etc), etc. This immensely helped with things down the line - I don't feel frazzled when I've got a million things to do b/c I know exactly what needs to be done (or which stages of editing my reports are in).
I also find that trying to write the background info same day (while waiting on data from the psychometrists - which can take a few days here) can expedite reports.
I sat down with my new supervisors individually and discussed how I had been trained and what I was hoping to get out postdoc. I have one supervisor who continues to look back at that and pushes me to work on those goals (e.g., not relying on an interview form, shorter / more concise reports, etc). So I encourage you to be open / up front about your weaknesses and goals for what you hope to get out of fellowship. I'm at a clinical site for neuro postdoc. I have a strong research background (which they knew coming in) and I expressed my desire to write a grant while on fellowship. They have supported with in this endeavor, but I had to let them know this was goal upfront (and that I wanted to save 1 day for research per week) in addition to my clinical goals.
Good luck!
