[BrianG]

The best way I can think of to get the max reduction in rpms would be to use a worm drive unit. You may be able to find a few surplus planetary gear drives and use a few in series (if each provides 10:1 ratio, only three are needed to get 1000:1 total), but I'm not sure those will handle the torque/wear. An R/C robot store should have all kinds of gear setups.

You generally gear for the max speed you would possibly want, and use a dimmer to give you ranges from 0 to that max value. In your case, you could also use it to get a little closer to your desired speed if gearing is not possible/feasible. Since you want 2rpm, I would get no higher than 8-10rpm with gearing and use the dimmer for the rest. Some expirementing will be required of course.