From 30mm dia and up I prefer to inflate a bag inside an aluminium tube that has been split in half and rejoined with hose clamps. Line the aluminium mould with packing tape and coat that with PVA. Blow the bag up with a compressor. Everything comes apart easily and the carbon tube comes out looking like a section of shiny black glass.
Under 30mm I coat aluminium tube in cadle wax and use it as a male mandrel. Once cured pour boiling water down the tube, the wax melts and and the mandrel is released.