I don't have a Manix, but when I saw the word "flaring" my first thought was a pair of ball bearings and a ballpeen hammer. Place one bearing on a hard surface, place one end of the tube over that bearing, place the other bearing on the other end of the tube, and tap it with the hammer.
Use a piece of masking tape to hold the bearings against the tube/knife so that they won't "jump" and roll onto the floor when you hit the top one with the hammer. It won't matter if there is a layer of tape between the bottom bearing and the base you use, or a layer of tape between the top bearing and the hammer. The tape won't be thick enough to cushion the blow and affect the flaring.