To do this I use moulding natural latex, mixing in some latex thickener. The latex thickener is good to use since it makes the latex thick enough to brush into the mould. Latex is naturally yellow to its colour, so it is a good idea to mix in some white acrylic paint into the latex to give it a good base to paint on.
Then I simply brush the latex into the mould, trying to get an even layer covering the whole mould.
When the whole surface is covered with ca. 3mm layer of latex i leave it to set. Latex sets in the contact of air, and you can speed the process up by adding heat, like a hairdryer.
When the first layer is set I add a piece if skincoloured powernet across the surface. I then apply another layer of latex on top of the powernet to make it completely sealed in the latex. The reason for this is to make the latex skin more durable, it will also make me able to sew the latex on to the suit without it breaking.
Once more, leave it to set, wait at least 5 hours until you remove the skin from the mould.
Then the skin is ready to be applied to the suit, and painted with acrylics. I repeated the procedure 6 times to have enough skin for the whole costume.