How would you recommend writing an evaluation of someone from another branch to use wording that would best reflects their performance?

I have been retired 20 years now, things have changed drastically BUT, I am betting if you contact the Master Chief Petty Officer of the Navy’s Office he/she would be happy to give you guidance. There are/were several Navy publications just for that purpose.

Very Respectful Submitted
Master Chief Hospital Corpsman (Fleet Marine Force/Surface Warfare) Cort Jensen USN-Ret

SGM (Join to see) Having written evals for employees from other areas of my discipline, I found that direct sentence structure which addressed the "what", "how", and "how well" worked to avoid confusion from the parent organizations. General avoidance of acronyms was also useful. Just my 2 cents.

For Marine fitreps there is a little more information needed to fully help. Are you being designated as a Trusted Assistant, RS, or RO. MCO P1610.7 is not very direct and leaves a lot of room for personal interpretation when evaluating the leadership traits, and more often than not it becomes a game of maintaining the average for the RS. if you are providing input i would suggest giving honest evaluations of the graded leadership traits and abilities. Being a joint command the Section I will have a few required statements. if you would like i can send a copy of my last section I, which is the only written out section of the Marine Fitrep.