I’m moving into a new, un-insulated shop and need advice on the best insulation strategy.  The shop has rough sawn 2×4 walls (full 4” depth).  It’s 25’x35’ with 12’ ceilings.  The exterior is metal, and the cladding is wooden planks.  I’m thinking about rigid foam between the studs, and then a layer of DIY spray foam over top of that, to provide an air barrier as well as get into the small spots.  I’m also unsure of what to do in the ceiling.  I’m thinking of vapour barrier, and then either blown in, or batts on top.   Looking for any suggestions.   Thanks!