Just take a long poker, like a piece of re-bar or something like it, and jam down through it repeatedly. The dividing partitions are brittle and will break into fragments easily and fall out.
I use sections of rigid conduit (aluminum) one end is ground to a one sided edge so when run down a piece of bamboo it will cleanly cut the node membrane free. It takes me about 20 minutes to remove all node membranes from a 10m culm. The important thing is to have the piece of conduit as close to the size of the culm interior size as possible but still slide through the whole length of the culm. I cut mine into 10m pieces then remove the membranes then split the culm into sections. Since I use this material to make fly fishing rods, I came up with a method that is not only fast but easy to do. Most of my bamboo is Tonkin, usually around 2" OD but this same method will work on most usable bamboo species, just size the "pipe" to what you have. I have also used solid rods to do the same job but they don't cut the membrane as cleanly and you almost have to be able to see inside to make sure you got all of the membrane cut loose. If you are working green stuff, removing the membranes makes for a much nicer "dry" piece of bamboo. You can also make flutes from bamboo by leaving a single node membrane in place you can even make a NAF type flute.
The ease or difficulty of punching out the node diaphragms can vary with species of bamboo and diameter. Generally the smaller in diameter are harder. (less than an inch (2/3cm) diameter). Usually one can use a metal pipe or rebar (used in concrete reinforcement and available cheaply in lengths at a 'HomeDepot' builders supply stores. It's best to use a size that is a little smaller than the inner diameter or it might get stuck, or crack the bamboo during the process. I always have several size diameters on hand. The other method is to heat the tip of the metal rod/rebar over a gas flame or whatever, till it is red hot, and it will easily burn through the node stops. Or after initially punching out the main portion of the diaphragm you can use the red hot tip to smooth the inside edges. This is a smoky undertaking best done outdoors. The other method is to use a long drill bit (often used for drilling lamp stands), with an extended shank, but these can be pricey. Cutting/splitting the bamboo in half, removing these node diaphragms and regluing the 2 halves is a lot of work. I would use this method as a last resort.
I read the answer to your question in one of the forums I visited. https://www.bamboocraft.net/forums/showthread.php?t=2639
Poke a stick thin enough to fit inside the bamboo, then put some sand in and then spin the stick like a drill.
