Insulation help for my garage with pics

hey Steve none of these other experts saw is that you don't actually have a soffit , you have covered tails so to speak which means as Nuttyprof pointed out that you need to vent each rafter bay , I would recommend installing a proper box soffit with venting every 4 feet or so and making sure they didn't block the bay spaces on the top plate , then there are a number of products available for creating the air space in the rafter bay but for rigid foil board you can just nail it to the surface of the rafters and tape the seams just don`t butt the 2 sides at the top leave both sides a couple of inches short at the top and then vent your gables ( which you should do in any case ) if you decide you want a little more you can always bridge the 2 sides with a wide enough strip of rigid using good old Tuck tape just do it below the gable vents .