I suspect most people would find this of interest...

[Alpha1]

It depends what you want to use the pressure pot for if you want to cast stuff that is shown in the youtube videoes using resins etc then you would use a garage compressor to pressure the pot. The pots are what industrial painters use they are modified for casting use. Or there are companies in the UK that build dedicated pressure pots but they are expensive.
Keeping it under pressure while it cures makes sure you don,t get any voids or air bubbles in the blank/work piece.
If you are using exotic woods or soft woods you want to force clear resins into the piece so you can turn it with out it tearing or breaking out in this case you would want to put it under vacuum so you need a vacuum pump.

If you think this is some thing you would want to learn about by all means pm me.