Greetings from Nebraska.
There are specialty tools made for pen disassembly. They primarily consist of a gripping tool to grip the blank without damaging it and a set of punches that can be inserted and tapped to push the parts out. You should be able to find "disassembly" tools on the vendor web sites like the "Pen Disassembly and Transfer Punch Set" from Woodcraft or the Disassembly and Punch Combo kit from PSI (which is currently on sale).
Typically disassembly like this would be done by gripping the blank with something that has a soft grip like a locking plyers with a piece of surgical tubing or soft rubber between the plyers and the blank in order to protect it. Then by selecting the largest diameter of transfer punch that will fit into the tube from the opposite end and tapping the punch to push the stuff out.
In a pinch, a rubber jaw on a vise or other kind of rubber protector can be used to hold the blank. If you do not have transfer punches, I suppose a drill bit may suffice. Insert the back of the bit into the tube and tap on the cutting end using a block of wood or something between the hammer and the drill bit as to not damage the bit. The specialty tools are of course better designed for the task, but in a pinch I have improvised in the past. Just make sure to use the biggest diameter punch that will fit into the tube (or through the adapter that was pressed in.
Of course there is always some risk of damage involved whenever one squeezes and hammers on things.
You might also google for videos related to pen kit disassembly. I know that Bob at RJB Woodturner has a video that uses Allen wrenches as temporary punches to disassemble a pen. I don't know if this link still works, but here is Bob's video (
https://www.youtube.com/watch?v=j_W7SX7jp8E). I learned a tremendous amount about turning by following Bob's videos.
Good luck with your attempt.
Regards,
Dave (egnald)