Alright this works for smaller scales and wargaming. Picky modellers might want to just ignore this.
Take a strand of wire about .5-7 mm (Mechanical pencil lead sized). Get a good long piece
You need a second piece that is a thinner gauge same length or a bit longer.
Attach both pieces side by side onto a table edge or something, now get a cordless drill and attach the pieces to the chuck. Now start the drill slow and spin the wire till you get wraps at however many intervals you want.
For different scales just get larger or smaller wire and spin more or less.
Now you can cut to length and wrap around a dowel or something round and place in your dios. It may not have physical barbs but it does represent razor wire fairly well especially the way light shines off the smaller gauge wire.
My real name is Cam.
Interest: anything 1/72, right now mostly sci-fi and modern
In progress:
1/72 Sci-fi diorama (link in my web)
1/72 Leopard 2A5
1/72 APC Conversion to a MEGA DESTROYER