Here is my bed. I was in a hurry, so I just glued the resistors to the base using Arctic Sliver epoxy. For the wiring, I just used stripped 14 awg copper wire.
You should determine how much current you can handle and work backwards from that. You want as much current as possible because the metal can take a long time to heat up.
Most people use resistors in Parallel because resistors in the 6-10 Ohm range are easier to find than resistors around 1 ohm.
If the current is very high you might consider using a separate power source and driving them through a SS relay.