How did you do the emblem on Asriel's robe? I've been wanting to do a cosplay of him too, but this is my first one and I don't really know who else I can ask
I hand painted it on using a stencil I made. Here is a step by step of what I did:
First I traced the emblem onto a thick piece of paper. I printed out the original design first, then put it under the thick paper, and used a bright light underneath the paper so I could see the design through it and trace it.
After that I cut the design out to make the stencil (since the paper was so think I used a box cutter, but this could easily be done with scissors).
After that I put double sided tape around the edges of the stencil. This way when I positioned it on my fabric, it would stick, reducing the amount of paint that could potentially leak under the stencil.
After the stencil was set, I used white acrylic multi-purpose fabric paint to start putting on the design, letting each layer dry for about an hour or two (sometimes using a hair dryer on a low setting to speed up the process), before putting on another layer. I did this around five times, if I remember correctly, until none of my fabric was showing through.
After this dried, I carefully pulled off my stencil. Any areas with discontinuity (to light at the edges, uneven, or where paint leaked through a bit), I fixed by hand, using thin brushes in order to make it even as possible.
After that dried, I heat treated the paint (be sure to test if your paint can be heat treated on a scrap piece of fabric first). First you place a thin strip of fabric over the painted design (preferably a cotton mix), and then you use an iron on the appropriate setting for your fabric (in this case my heat was high as my fabric is wool), and iron it. This can help (or so I’ve been told) set the fabric paint. I hear that this can be done by throwing the fabric in the dryer as well.
Bam! You now have the emblem on your cosplay. There are many other ways to get the design on, but this one was easiest for me due to the type of fabric I used to make my cosplay.
For some visual help, I have attached a few pictures of my work progress that are originally from my Instagram.