If you didn’t fly 25 hours with one single PIC, prepare multiple letters as appropriate. In my case, I had to prepare three different letters. The total hours combined was more than 25 but that wasn’t an issue.
I then sent the letter to each captain I flew with, through Docusign, as you get three free documents to have others sign digitally. I wanted to make it as simple as possible for them.
Logbook Excerpt
While the letters themselves could possibly be all you need, it’s best to provide an excerpt from your logbook highlighting the specific flights you’re referencing.
I use ForeFlight as my primary logbook so I simply exported a single-page logbook showing only the specific date range I referenced in the letters. Then I used the Shape tool in Apple Preview on my Mac, to create a border around the relevant entries.