I think what we need to clear up here is the difference between terms, and their specific applications.
When you're making a rubber mold, you'll get a lot of good use out of a vacuum chamber. By reducing the air pressure inside the chamber, it forced ALL the air to equalize, pulling all of the air out of the rubber too. You CAN use a vacuum chamber to degass your resin, but typically your pot life on resin is so short, you run a good chance of it catalyzing before you're done degassing it. You're better off mixing your resin by hand. Make sure you don't whip a lot of air into it, just use strong, deliberate strokes to ensure even mix, be sure to scrape the sides, and double mix if you need to.
The use of a pressure pot does the exact opposite of a vacuum chamber. Instead of pulling the air OUT, it increases the pressure in the pot to the point where all of the air bubbles (remember, air is compressible) are minimized to an imperceptible size. The pressure pot also forces the resin into those places where surface tension can affect the viscosity of the resin (like the tip of the nose, ears, fine details). The only thing is, though, that a pressure pot is NOT something you can build yourself. You're filling this tank with a LOT of pressure, and if you do anything wrong in its design, it WILL explode like a bomb. Purchasing a pressure pot is an investment, but it will help ensure that your casts come out as bubble-free and detailed as possible.
Tip: If you pressure-cast into a rubber mold that was not also pressurized while it cured, your rubber mold (which still contains air pockets) will deform while in the pot, warping your resin casts. When you open the pot, the rubber will bounce back to it's original shape, and you'll be left wondering why a "perfect" mold is putting out such bad casts. If you're going to pressure-cast your resin, always try to pressure-cast your rubber mold too.
