Each sculpting medium has his own features which means each one requires a different approach (read technique) and tools. To successful use whatever medium you need first to understand how it works and for what it is intended, something you will only learn by experience.
Besides that you also need to understand if you are a modeler or a carver or both. Modelling and carving require different techniques and tools, most of people is used to say "sculpting" tout-court but "sculpting" per-se does not mean anything. Polymer clays like Sculpey, Fimo, etc are perfect for modeling while two parts epoxy putties are the best for carving, it is obvious you can also carve baked Sculpey and model fresh putty but it mainly depens on your ability.
Regarding the Magicsculp, in my personal opinion, it is one of the best epoxy putties out there, I do almost all with it and I dont think there is something you cannot do with it. Just keep in mind that it is almost unusable just after mixing it, you need to wait 5/10 minutes at least before messing with it. Folds aren't the most difficult thing to reproduce, they have the same difficult level of anything else, it's just a question of vision, I mean you only need to look at the real thing and sculpt exactly as it is. Take a picture of whatever old roman bust (something like
this) and try to make an exact copy, no matter how many attempts you will need, I did it way ago for
this piece using as a reference a
Bernini's sculpt and it helped me a lot in understanding how to fold.