You can separate a significant amount of fiber by hand.
The trunk of banana, once sliced open, is very easy to pull apart. Though you can't see it very well in this picture, the inside of the trunk is loaded with beautiful fiber.
Now you have to start processing the fiber. First, separate as much of the fibrous material from the non-fibrous material by hand as possible. For this tutorial, we will use banana stalk. Banana stalk is full of beautiful fiber. The inside of the stalk consists of alternate layers of fibrous and non-fibrous material. Much of the stalk can be used.
With other plants, the fiber may be in an outer layer, with the inner part of the plant being mostly non-fibrous. With grass, for example, the bulk of the fiber is near the outside of the stalk.
If possible, you should cut the sections of the plant you are going to use into four to six inch lengths before moving on to the next step. Once you have separated as much of the fiber by hand as possible, you are ready to proceed to step 3.