Hi Andy, we use Sta-Warm pots for pouring our Stick worms (Del's) and it takes about 8-10 seconds to pour each worm. We use LOTS of salt in this pot and have yet to see a rust problem of any kind, might be because it get cleaned out after each use. I fear that using a pressurized pot will put a person at risk of getting sprayed with hot plastic, as I understand it the operator would have to hold the mold against the nozzle...I would be cautious with that one. We also use Rite Hete pots to dip our tubes from. An excellent choice for dipping, not pouring. We got a heated nozzle attached to one Rite Hete pot and its not the best idea for pouring into one sided molds as the nozzle is too close to the pot.
As for a stirring device, get a drill press and it will more than suit your needs. We purchased a model that runs between 240 - 2000 RPM. You can set it to different speeds to suit the level of plastic in your pot. An example using a 2 1/2 gallon Stawarm pot filled to 2 inches below the rim - 700 RPM, 1/2 filled 450 RPM...this allows you to stop any cavitation cause by running at too high a speed with too little plastic.
Hope this helps