It sounds like a lot of work and it is looking like it will be even more.
In order to be able to hang drywall for a ceiling, we need to have 16” centers (our garage rafters are currently 24” centers). Of course if I want to put anything up there for storage, I’ll need to have even closer ones, so I’m thinking of just doubling the amount we have and going with 12” centers.
Here’s the work run-down: Add rafters & supports, add pull-down ladder for storage access, put drywall up for ceiling, add insulation and plywood for storage flooring, check to see if additional ventilation is needed. Mud and paint ceiling.
It’s a big list. I can see getting the extra rafters up over the fall, but somehow I think the rest of it is going to have to wait until next spring.