Tojo72 has given great advice regarding organizing and running a GB.
One thought I have is when researching previous GB’s, go back several years-I remember several WWII era & battle group builds in my early days here. In my opinion, it seems Group Builds have not been as numerous in the past few years.
Here is a Midway GB from 2017 that might be a good guideline.
https://forum.finescale.com/t/battle-of-midway-group-build-3-june-2017-7-june-2018/242009
I’m planning on joining and will be more than happy to help if needed.
Bob