First, use powder instead of flour. Flour and water make a paste that turns into a mess, especially when it dries. Also powder really helps getting the tire on and not so much when you add air.
you dont need flour, you put the new tube in air it up let it down, then air it up again ,this allows the tube to get all the folds out and sets the tube in proper place. When a tire sits and goes down you cant just air it up and ride. You have to air it up while checking the beads are seating properly.