Heat the entire cylinder/glowplug with a palm-sized mini-torch, and then chill the plug with a chunk of ice or a blast from a spray solvent to shrink the glowplug.
Still no movement? You may need to make up a motor mount to clamp the motor down for better purchase...preferably in a vice (the motor mount, not the engine).
If you heat the engine with a bigger source of heat, you may need to wrap your venturi body with a cool, wet rag.