I've have just switched from bf to ff (for various reasons which I won't go into here) and am so confused about how to prepare a bottle when you are out and about. All the literature says you need boiling water to sterilise the powder but how do you cool it quickly if you are out? I wondered if I could mix the powder with cooled boiled water and then top up with boiled water from a flask? Will that be safe enough? Am I just being dense....hundreds of women ff their babies out and about so there must be a way to do it safely!! Dd is 8 weeks so I don't want to do anything that could give her an upset tummy hence the stupid question. 