I didn't think about taking pictures as I did this, but I've got a second wig I need to attach horns to (for when Red wants to have different hair), and I'll grab pics from that. Besides, there will be better contrast with that, since it'll be black/gold horns and a red wig, instead of black/gold horns and a black wig, where even *I* could barely tell what was what through most of the process, much less take illustrative pictures.
Cutting the description so it doesn't clutter f-pages.
There are a few steps that "have" to be done before others (like Location and Silhouette before Wig Base, Silhouette before Horn Base, etc), but this is just the general flow.
Horn Prep: If you're going to paint, glue, do whatever to the horns, do it NOW before you even start messing with the wig. I spray painted mine to be a satin black and dry brushed gold over it to highlight some of the ridges and texture of the horns. Tip on dry brushing: wipe as much of the paint off the brush as you can. You'd be surprised how far a little bit of paint can go.
Location: You're probably going to need a friend for this, though you can do it by yourself. Put on the wig, and position the horns to be where you want them when it's all said and done. Get your friend to hold the horns in place while you mark the position (generally the two "corners" of the horns) in the wig with tiny mini-chip clips. When you take off the wig, be careful to not disturb where those clips are, since more than likely, you've got your own hair in those clips.
Silhouette: Put the flat open side of the horns down on some cloth, and trace the outline. You're going to need two of these for each horn. I used cotton for one, and ripstop nylon for the other. The cotton goes underneath the wig, next to my head, while the ripstop goes over the wig, right underneath the horns.
Horn Base: I hot glued the ripstop nylon to the bottom of the horns, covering the open space. I then trimmed the sides if there was any overhanging so that the nylon and the horns matched up exactly. Don't pull the nylon completely tight like a drum head, it won't sit right on your head if you do. Leave some play in it so it can adjust to the contours of your skull.
Wig Base: Match up the cotton corners with those markers you put in earlier. Sew the corners into the wig, knotting them in each spot. Don't make it a continuous piece of thread, cause then you'll have to worry about tension and tangling and stuff. Just a few stitches at the corner, knot it off, and cut. Also do the same for the two widest parts of the silhouette. Now you know *exactly* where those horns are going to be on that wig, which takes a lot of the guess work and uncertainty out of the rest of the steps.
Exposing Wig Base: I couldn't bring myself to cut the hair above the wig base, so I just parted it off to the sides as neatly and precisely as I could. I used more tiny mini-chip clips to hold the hair there after I sectioned it off. At this point, I could see the wig base fairly easily since all the hair is out of the way. This eliminates any loops in the wig from gluing down hair that originated somewhere else and is now permanently fixed to the horns.
Gluing the horns in: The scariest point in this whole process, the absolute moment of no return. So no pressure. :D Anyways, I started at one corner of the horn, covering a small area with hot glue, and matched that up with the exposed wig base, pressing them both together firmly and burning my fingers slightly. I accept that's part of the price of getting the horns into the wig securely. I covered the next little section of the horn base with hot glue, and pressed that to the wig base. I continued this rolling the wig up to the horn process of gluing till the whole horn was secured to the wig. A few parts along the edge weren't in there securely so I put a little hot glue on those areas and pressed them tightly together. While there was a little hot glue visible along the edges, I could pull some of that away without damaging the bond.
Finishing: Take out all the clips and style the hair over the horn. You shouldn't see any of the horn base or the wig base from the top of the wig, and even the seam of the horn to the wig should be entirely covered with hair that you parted out of the way earlier.
Same pain, other side, and you've got a horned wig.
x-posted in my journal and fakehair