Wow, you made all of that?! Those clothes are seriously amazing; it looks like a real life-sized outfit one could wear! Awesome job on this, it turned out really beautiful (and you put a lot of time into it too!)
Frankly? With lots of curses, trial and error. The armor is sculpted out of 2-part epoxy putty called Apoxie Sculpt. I will post a tutorial with hints on making shoulderplates. Parts are connected with leather strips, and his cloak has a velcro on the shoulders.
Do you mean you have an action figure Sephiroth? Or do you have a BJD? I may suggest Den of Angels forum: [link] (the registration is rather tricky but it worth it). There are a ton of tutorials there, including some tutors on shoes I composed.
I made a symmetrical prominent shapes out of plasticine for sculpture and then put a layer of Apoxie Sculpt Putty (~ 3 mm thick) over them. After Apoxie cured I cut the edges, sanded it smoothly, added reliefs, sanded more, painted etc. As shoulderplates are symmetrical I needed only 3 base shapes, not 6. Apoxie Sculpt is a 2-part epoxy putty designed especially for sculpting. It can be called plastic, yes, but no mold were used.
1. No, I made some simpler stuff first, like this mug: [link] Than I made this head: [link] And the armour is my latest work))
I like Apoxie Sculpt very much, it's rather simple to work with. They put an instruction directly on the packaging. You just take 2 equal amount of each component, mix them thoroughly, then sculpt whatever you want (working time is 2-3 hrs) and then let it dry about 1-2 days. It becomes hard and strong.
2. Yes, many modders use Apoxie Sculpt for modifications, and it adheres wery well. It can be painted or blushed with pastels to match the skintone. Though, after it's cured it could not be removed from resin easily, just sanded out only.