I use an "A+B" epoxi mass for artisans,45 minutes, someting common and cheap. First is a skeleton of stretched plastic (or rolls made with the same mass) 2-3 mm (not wire for me). Just legs and thorax(not arms initially)sometimes I put the head in the skeleton, usualy I take heads from another plastic figures, except when a special facial expression is needed (smile, cry etc), or te face is very special,(like the face of Schwarzenegger). Then i work with the epoxi mass starting with the legs (boots, then throusers), then the thorax (first the "basic" like just a naked chest,later the belts, holsters, and then the jackets and pokets etc) finally the arms, with stretched plastic glued in the chest I the position that I like. For moulding the tools are surgeon's disposable blades for scalpels, pins, and for the buttons a disposable needle (depending of the gauge, I used this for the belts of the vehicles too), hairbrushs, cause the mass is stiky and this make dificult the movements of the tools, alcohol or water is used to lubricate the surface.Abouth weapons, sometimes I teke it from common figures or I make it wit plastic. Hans are allways a problem, when the hands are over a fix surface (for instance a rifle, or a wheel) is easy, but for the hands are in the "air" (like smoking for instance) is a pain in the...well, you know.
Finally like everithing is just a question of practice.
But when we have a good plastic figure, better don't spend the most valuable thing for the modelers...time. (LOL)