I have farmed a shop inside my pole barn. I have 6mil plastic under the concrete by no insulation. I do not plan to to heat and cool it very often. Also, I was given 12 rolls of unlaced R25 fiberglass insulation. The siding has been up for over a year it does not leak. My plan is air seal the exterior walls with caulk and cans of spray foam. I also plan to use a 6mil vapor barrier over the fiberglass and behind the OSB interior walls. The rolls of fiberglass are 6 feet by 25 feet and 8" thick. Can I install the fiberglass between the post and the new stud wall and leave the stud cavities empty or do I need to cut and fit in inside each cavity?
If I am wrong on all counts, how should I install the fiberglass. I have a friend coming over in the morning to help, so I'd like to do it right the first time.