Pumping at work - Bra question

I have 3 more weeks before I have to go back to work. Just started thinking about my clothing for work. Should I wear a regular bra & just change into a pumping bra when I pump? Or just hold the flanges on my boobs? Or maybe wear a pumping bra underneath a regular bra? My boobs are huge so I want to make sure I have good support. What do you do?