Simon, No problem going back over arms/hands.
ARMS Put a thin layer of putty or clay over your armature wire. After this is cured add another layer. I would then add more material that starts to define the main muscle masses. This may take another 2+ layers of material, depending on how big/thick you want your figure's arms to be. You should be able to build the arms with the half sleeves on the figure, it might even make it easier than doing them in two separate parts.
HANDS This was always the most difficulit part for me to do. Though I still find it trying at times, I admit it has become easier to do. I initially build the hand minus the fingers. You could use an armature for the fingers though I biuld the fingers separately a section at a time. For example, the middle finger, I would make three separate sections for the finger. The first rolled out section is attached (glued) to the main part of the hand, with the next section being glued to this and so on. I then add two-part epoxy to where these sections join one another for added strength.
I hope this helps.~Gary
