Making formula without prep machine

Apologies in advance if this is a stupid question!

Will be going abroad to visit family and debating taking prep machine with me. Ideally wouldn't as it takes so much space in the suitcase but how do you make formula without it?

Nhs and formula packet instructions are quite unrealistic, I'm happy doing it in the day time but surely it's unrealistic to wait for the kettle to cool down for 30 minutes when baby needs a feed at 3am. Baby doesn't like milk straight from the fridge either so can't easily prepare several at a time and store in the fridge.

Can I diy prep machine method by adding a boiling water to formula and topping up with cooled boiled water? Not sure if this is safe? And does it have to be 70C or is freshly boiled just fine? Can't find any explanation why it has to be 70 degrees.

We will have ready made bottles for days of travel but can't take this many for the whole stay sadly.

Am I missing any other obvious ways here? Sorry if this is a stupid question, I'm too reliant on prep machine at home!