I just started with small scale sculpts a few months ago. As far as the armature wire, I personally use aluminum foil that I crumple into the shapes and then sculpt around those. Depending on what you are doing, I'd say a good rule of thumb would be separating all extremities from the torso and molding them separately. Also check and avoid things that would create a really concave area in a mold that would easily trap air bubbles. Got a few picture examples of 2 busts I made. The Pred is 4 pieces (head, torso/base, plasma caster, and dread molds)though in retrospect I should have made it 5 and molding the medpack separately, due to it creating that concave surface I talked about, plus while demolding it ripped the mold into pieces.
On the other hand I was able to do my vampire lord in one piece due to the general lack of concave surfaces (although the chin does catch air bubbles).
Hope that helps a bit.
Ps. Depending on how small the pieces are you are trying to cast you may want to plan and cut in small channels in the mold that will let air escape more easily when casting it (super important when molding and casting dreads and Plasma casters).
