I added all my expressing from one day to the same bottle - if I hadn't already used it as a top up that is I'll admit, I rarely had a full feed available in a bottle for DD in the early days, just top ups.

I used to warm my EBM by sitting the bottle in a mug of boiling water for a couple of minutes. When we went out, I'd usually give EBM to DD at room temp so if you can plan ahead and defrost it early, that could work.

A friend of mine took a thermos out and about with her and poured the hot water from her thermos into the lid of the thermos (you know how the lids double as a mug) then put the bottle in the lid (mug) to warm it. It worked a treat!

As for DD taking the bottle, well she took it no problems - thankfully. We had a long list of feeding issues over the first 12 weeks or so, the first being that she has gained very little weight in her first 2 weeks (only 60g ) so she was taking EBM at less than 3 weeks of age.