How to sterilise

I’ve just bought the Nuliie double breast pump as I’m going back to work in June and I need a discrete pump to use whilst working. I have read the manual and it doesn’t recommend sterilising in the microwave (I have a Tommee Tippee microwave steriliser). What is the best way to sterilise? After each pump at work, can I just pop the pump in a zip lock bag and put it in the fridge, rather than sterilise each time? I’ll probably pump 2 or 3 times at work, depending on how much milk I get from a double pump. Getting a bit overwhelmed with the idea of pumping. I pumped for a couple of weeks in November but this was only once a day and the pump could go in the microwave steriliser, which was much easier. I just hate that it is not hands free. Any advice please on pumping at work. I assume I can sterilise the bottles at home first and then pop them in a ziplock bag still wet?