When your feet hurt after a 12 hour shift it can be caused by the weight being put on your feet.
When you need to do a lot of standing on your feet that pressure can cause pain in the feet which is normal.
I used to work 12 hour shifts where I had to be on my feet a lot and when I got home my feet were so sore for at least the rest of the night and all I wanted to do was get a shower and soak my feet in water and then lay in my recliner with my feet up.
I would recommend getting some gel inserts for your shoes that help add cushion to your feet.
My sister is a nurse and she is on her feet for 12 hours and sometimes 14 hours per day and she had hurting feet and was about to quit the nurse job but someone recommended her some gel inserts for her shoes and feet and they worked great.
She now can be on her feet more without as much pain.
The pressure on your feet from your weight puts pressure on your nerves and bones which causes the pain.