Best way to collaborate on grant writing with other orgs

Hi everyone, I’m a new grant writer at this nonprofit where I’m the only one doing the grant writing work. My org is applying jointly for a grant with 2 other orgs, but we will be the lead applicant. How would you suggest going about doing the grant narrative? We have a past grant narrative we are using as a foundation then we will adapt it to this grant, and I have a meeting this week to discuss next steps but im kinda nervous about how should i do this. Usually I just start writing the application and have the ED review it but i have never worked with outsiders. Any tips on the process of how to work collaboratively in an efficient way with outsiders?? How would you lead this? Thanks!!