I am probably not the best person to be asking since I am still learning myself, so take this with a grain of salt. Your best bet is just to observe metal objects in real life or find references. But I hope this at least points you in the right direction!!
1. Being passionate about your art
Foremost, the artist must have a passion for their art and everything that is associated with being an artist. Why? Because there will always be barriers to being an artist… but, if you are passionate about what you do, these issues will be…
For anyone who wants a reference of the DMMD characters, be it drawing or cosplay. Here’s Aoba, Ren, and Koujaku.
These are scans from the Official works (credits to whoever scanned them). I just cropped them and made it not so faded looking.
This is great omg