This is how we did it in the early days, based loosely on hour the perfect prep machines work with a shot of hot water to sterilise the powder followed by cooled boiled water to make up the volume for the whole feed:
Get a cheap kettle for use in/near the bedroom, have it somewhere you can't kick it over by accident.
Get a formula dispenser like this this and measure out how many scoops you will be wanting for the feed (saves having to keep count when half asleep.)
Have a few spare bottles (whatever you are using to feed if you have enough spare, or grab some from ebay and fill one or two with freshly boiled water, lid on loosely. These will provide you with a supply of cooled boiled water in a few hours when you need them.
When its feeding time boil some water, you want enough hot water for 1/3 or the volume you will need (eg if its 5 scoops of formula you will be using 150 mL over all, so you need 50 mL freshly boiled water). Add powder to the freshly boiled water and swirl gently to dissolve. Then add 100 mL of the cooled water from earlier. (Don't forget to empty and refill the bottle with water from the kettle so you have cooled boiled water for next feed.)
If in the middle of the night it's difficult to see marking on bottles you can always weight the water (we have digital scales with larger readout so i can see better without glasses) 1 mL of water (not formula made up, just water = 1g, so 50 mL = 50g).
This way takes 5 mins, and you can always cool further by running under a tap for 30-60s, as opposed to 10 mins if using all boiling water.