Epoxy does not bond well chemically to ABS or styrene, IIRC.
To make it stick well making a "mechanical" bond, you need to thoroughly roughen the surface with sandpaper.
I've heard the polyester laminating resin (like regular cheap fiberglassing resin) works well. It dissolves the surface layer of the the plastic, so it makes a kind of solvent weld. I'm not sure how thick the plastic has to be for that to work right, though. For really thin plastic, the solvent (styrene monomer) may soak too far through the plastic and make it get funky. (Wrinkles, warping, etc.)
I know people use it for gluing stuff to relatively thick ABS for non-costume stuff. For that kind of thing, it apparently sets up quick enough to hold the shape while the solvents work their way through the plastic and evaporate.
If you try it, let us know how it works out.
I'm curious whether Plastic Weld actually works better than other epoxies. Many epoxies are claimed to bond ABS or styrene, but my impression is that most of them don't actually make a good chemical bond. (And whether the package says it "works" for those plastics is more a matter of marketing than truth. Most of them sorta do, sorta don't, i.e. pretty good mechanical bond to well-scuffed stuff, but no chemical bond.)
Plastic weld may have additional solvents in it to get an actual solvent weld effect, but I wouldn't be suprised if it doesn't.
BTW, if you're using epoxy, I've heard it's a good idea to swab the surface lightly with acetone just before expoxying. (Lightly, though; too much and you'll melt it.)
