Yup, springtime!
There are a couple ways I would consider doing it, depending on climate and budget/availability
I am building in Tennessee, so mild winters but humid summers. I plan to use low-e or reflected. A roll out insulation and vapor barrier between the framing and metal. It is enough to stop most condensation and thermal bridging. Then I will use rock wool because it is more mold resistant than fiberglass. There will be venting between the metal and low e.
If I were in a colder climate, I would use spray foam. It’s the cheapest way to get HIGH R values when built planning for it. It is a little gicky but all commercial insulation is and spray foam is probably the lowest embodied energy. There is a ton of diesel wasted moving around bulky insulation.