If you are using storage bags, try getting one with the nozzle and twist cap instead of the zip lock variety. Kiinde has a great storage bag for easy pouring and storing of breastmilk. You should definitely give this bag a go.
Best to express directly into the bottles. And take out from fridge direct into warmer. That will ensure nothing every drops and gets wasted :)
Heat up the milk directly in the storage bottles then pour them over the feeding bottle.
NYC Daphne