I just use breastmilk storage bags I bought from e bay. They're sterile and cheap.. No idea about using ice cube trays?? Not sure how much a 4 month old drinks, but my DS has 150mls down his NG tube.. This has been built up gradually though because he wasn't taking that much from my breast.. I started giving him 120ml and built it up from there. I have no idea how much they 'should' be having. i am pretty sure you can wash bottles in the dishwasher.. I don't have one, so I just wash them in hot soapy water then chuck them in a steam steriliser.