My DS was bottle feed from birth and from my experience and research everyone has a different way of doing things so its really about finding a way that works for you and that you are comfortable with.
You should only keep a used bottle of formula for an hour so if he starts a feed at 10.30, you should tip the milk out at 11.30 although after about 15 mins I would be putting it back in the fridge.
I use to boil the jug in the morning, leave to cool and then fill my 6 sterilised bottles with the amount of water needed and then put in the fridge. I found this heaps easier.
I would then get the bottle out of fridge and heat in microwave (I had a really good play with our microwave to work out the exact time it needed), add formula, shake really well and feed. That was the quickest way for me and meant it was only 1-2 mins of screaming rather than 5 or so waiting for the bottle to heat in water.
I know lots of people say not to heat in the microwave but I was comfortable doing it as I had a really good play first and always shook well to avoid heat spots and tested on my wrist.
When we went out I would heat the water in the bottle and put in a insulated bag and then take the formula in a travel dispenser and mix and shake when needed as the water was always at the right temp.
Biggest tip though is to get your child to drink formula at any temp. Make life 10x easier as they get older!
As I said at the top, everyone has their own way of what works and what they are comfortable with so just go with what works for you