I use 2 pieces of 1.5mm round copper wire to help me get the shape I want and to support the roundness of the tube and prevent it from collapsing under the pressure. Each wire is about 40mm long. I use copper because it is fairly soft and the wires can be straightened after making each bead and used again for the next bead. The wires are inserted into the tube so they meet in the middle of the tube.
Place the tube with the interior wires against the mandrel and with your fingers press the tube against the curve of the mandrel starting in the middle of the tube and working towards the ends. If you start at the ends you risk getting a pinch or sharp apex in the middle and the aim is to get a soft curve. This tube is so soft and easy to form that you can do a lot of the bending just with your fingers, but the very ends of the tube are hard to get to the right shape. The small thick wire pieces give you a lot of control over the precision of the bend - how much bend and exactly where to bend.
Once you have the main bend around the mandrel you can use the pieces of wire to bring the ends around a bit more to complete a nice curve shape. I have the wire just inside the end of the tube about 5 mm depending on where I want the curve to increase. This process is best done with lots of small changes because you are trying to get both ends to be the same and the entire curve shape to be uniform so the bead looks balanced. If necessary you can also use round/flat forming pliers as a mandrel to coax the tube around.