Edit: Some people may be allergic to latex so PLEASE be careful when working with it the first time! wear gloves and work in a ventilated area! a mask could be a good idea as well
Okay, I should have explained this looonnngg ago, but here we go.
First of all this method is not mine, I got it from Sidsel who got it from another cosplayer, I’m not sure who. She also helped me make my pair of fins, but it’s actually really easy and simple.
All you need is some wire, tinfoil, a hot-glue gun, liquid latex(you should be able to buy this in just about any hobby shop), an old paint brush for the latex and of course your grey facepaint.
Use the wire to make the a skeleton, start with 3 pieces; one long(green), two smaller (red and blue). make sure they’re longer than what you need, you cut away what you don’t want after you’ve glued. Glue them together.
Now cut out ONE piece of tin foil for the front. An easy way to measure how big this piece should be, is to put the tin foil on top of your skeleton and draw the shape you want. Leave some space by the edges so you can wrap it around the (green) wire. Glue again. You can use a wet finger to model and smooth the glue while it’s still hot.
The “hook” for attaching the fin to your own ear is just another crooked piece of wire, glued to the beginning of the fin. (so you wear them around the ear) To make sure the sharp end of this piece doesn’t hurt you, curl it up and fix it with a drop of glue.
Now you should have the base of the ear, all it needs now, is layers of liquid latex. If you want cuts and such in the flesh, like i did, carefully cut the tin foil so the edges are uneven. Put the latex all over both sides of the fin. Make sure each layer is dry before you put on a new one. You should use at least 6 layers, the fin needs to be nice and stable and you don’t want the tin foil to break.
When they are all dry and sticky, you can use your normal troll paint to colour them and perhaps tint them in the blood colour if you want. Remember the backside too, but only the parts you might see. Use powder to seal everything like you normally would. The fins should now have a nice, smooth, skin-like texture to them. No sticky parts, if there is, use more powder.
This method actually works really well for pretty much any ear! Trust me, I have the smallest ears you can imagine and still the fins will stay on, if i play around with the hook a bit and use skin glue to make sure it stays where I put it. Use your wig to cover the end, so it looks more natural.
And that’s it! It’s really not very hard, you just need to have some patience with the latex. Good luck, and enjoy!
P.s. I use GRIMAS make-up mixed white and grey. If you don’t want to buy the expensive pro transparent powder for sealing , baby powder works just as well and you can get it anywhere! just remember it’s white, not transparent and might make your make-up fade a bit, so i recommend having some transparent powder for your face.