Prepping bottles to go

Ok I have twins - almost 4 weeks. We haven’t left the house too much but will be soon for longer periods of time. Best way you all prep bottles? They could eat every 2 hours right now. At home right now we mix the formula and fill the bottles and warm them up in hot water. When I pack the bottles to go sometimes they spill or I have to make sure to have them in ice packed coolers for the diaper bag. Easier way with formula? Prepping the amount of powder ahead? Ideas? Especially since there’s two!