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Pressure pot: depends on what you are casting. If solid resin, not necessarily required. If "mixed media", probably required.
How: pour equal amounts by weight of part A and part B into separate cups. Mix your colorant into part B in such a way to minimize bubbles. (optionally, degass part B by "bumping" or vibrating), Mix A and B together minimizing bubbles and pour into your mold. (optionally, put in pressure pot at no more pressure than pot is rated for). Wait 10 minutes, remove, drill, glue, turn, assemble.