Carl,
That is excellent value on the vacuum pump.

I like the paper tube method, I didn't realise you could unravel them from the inside.

Another variation of your method could be to cut a slot down a length of plastic conduit. Insert a strip of material like aluminium into the slot with some spacers between in and the inside wall to hold its edge flush with the perimeter of the tube.
Put a layer of packing tape over the packed slot to seal.
When the layup cures pull out the spacers and the strip of aluminium which will allow the plastic tube to reduce dia and come out. There is a bit of setup but may pay off if you are likely to use it again.
Just another way of skinning the same cat.
Regards,
Phill