I just use an old 2x4 with some small nails in it. Works just fine for me.
2 Nails on one side. One holds the spool of wire, the other is the wire "stop", and is in the center. Then a screw with a small spring (like from a pen) on the end of the other side (over the edge of the surface where you will be building your brushes. I also added a little notch on the edge of the wood that holds the wire in place in the center.
Wrap the wire a few times around the nail in the center and then run your wire down and catch the wire on the spring of the screw, leaving a few inches of extra wire between the spring and the spool. Notch the wire back on the spool and let the spool hang or chill on the desk or whatever. Build your brush on the wire now laying flat on the 2x4 (waxing the wire helps here). Insert your dubbing loop spinner in the extra wire, un-notch the wire from the spool, and run it back to the nail, keeping tension with your dubbing loop spinner. Wrap the wire around the nail again, notch the wire, and place the spool on the other nail. Twist up your brush until the wire breaks (or when I know it's tight enough I will force it to break with a quick yank).
Boom, brush done. Table can probably built with stuff you have laying around the house and/or garage, i.e. free!