Stuff the cactus firmly. A Detail Stuffing Tool (www.planetjune.com/tool) is perfect for
this, but if you don’t have one, try using an implement that is the same width as the inside
of the stalk (e.g. try the wrong end of a pencil or wooden spoon) to force the fibrefill
inside, a little at a time.
If the stuffing isn’t even, smooth it out by rolling the piece between your hands until it is
straight and the same width all the way along.
If the cactus fluff looks squashed after stuffing, re-fluff it with the wire brush.