[KingOfCheese]

Not sure what you would make the mold out of, but you may need to make it so you are able to attach a drill or something similar to it to spin it.
Molds that only require detail on one side (such as bases) are quite easy because the air can rise to the top where the detail is not as important.
With something like a metal model, you will need to be able to spin the mould so that the centrifugal force pushes the liquid to the fine points at the edge of the model (such as swords etc).

 

[KingOfCheese]

Yep, as B&K said, Resin is by far a better option for making models from molds.

If you have a look on youtube there are several very informative videos about using resin.
There is one series of videos where someone makes a mold for bases. He covers everything from what products to use, how to make the mold, how to use the resin, and gives lots of very informative tips along the way as you watch his progress.
If you are looking into using resin, i would highly recommend it.

EDIT: When using resin, having something that vibrates lightly helps the air bubbles rise to the surface. Sit the mold on it while the resin is setting and you will lessen the chances of air bubbles.
Just make sure its a light vibration and NOT shaking (DONT put it on top of a washing machine for example).
Oh, and try to keep the "vibrating" jokes to a minimum lol.