For characters with smaller hitboxes, you really want to get them as high as possible before using Jakou. For larger characters (like Tager) you can get away with it more, but you really need to take advantage of those little hops in the air after ~A chain followup and hit with Jakou as high as you can. This'll make it easier to connect Houtenjin after dash-in 3C.
Yeah, that first combo must have been written wrong, because unless you are Tao, you can jump cancel twice in the air.
When you are high in the air, the best combo I've found is jD~D > jB > djCx5 > dj214B
However, if you are close to the ground, you can go jD~D > jB > djCx5 > [land] 2C > 4D~D > jCx5 > djCx5 > dj214B