First thing a shop will do is roll up your windows, especially in the middle of winter.
Yes, they all use a meter. It's part of their equipment.
Once you have a rejection logged into the system, nobody will pass you.
The law is Net VLT. They don't care if you paid for 40%..if you meter below 32 you technically fail.
I have spare untinted glass I use to get my car through inspection.