Hi Bart. Although I am not a Markham Researcher, I applaud your initiative. I have done a couple of "projects" similar to this and have a few "organizational shortcut" suggestions already in place. (Hindsight is 20-20).. If you want more, send me a private message.
1. Develop a couple of "generic" messages - one for Profile Posts (max limit) and another for Private Message (longer) Send to all profile managers explaining who you are and what you are trying to do; recruit them to help you; invite response on any concerns, questions, or if they need further explanation. (You could do this with a trusted list request and use as a followup to determine active vs inactive)
2. Define a "Project" for your early profiles (to about 1700-1725) and/or category(s) (for all)
3. Search out your dups and initiate merges to lowest LNAB (be sure to check undated profiles also and/or insert DateGuess)
4. Make a template you can copy/paste with generic info like project, category, vitals, and source(s)
5. Start with earliest profile and work down - spouses, all children, etc.(search for these - may already be on Wikitree - unattached or incorrect)
Good Luck. If you need more specifics, let me know.