RS485 Protocol

TL;DR Can't find unknown RS485 baud rate

I need some help.
I have a lighting controller (brain) that controls some dimmer modules. The circuit board for the brain is labeled RS485 between the brain and the dimmers. I want to replace the brain with my arduino.
The first thing I need to do is "hack" the protocol that it uses so that I can duplicate it with the arduino.
I connected up my FT232 USB to Serial converter set to 5v after finding the ground and send pins with my multimeter and tried every baud rate I could find published online as a typical baud.
For baud of 57600, 76800? and 115200 I got random characters (question marks, question marks in black diamonds... Etc) for everything else I got nothing.

What could I try to find the baud rate and format that I could duplicate? If it were hex or some other form would that effect how the serial terminal reads it? Would an incorrect voltage effect the ability to read?
It's a proprietary device so I wouldn't be surprise if it weren't a standard baud rate but could it be anything? What are the limitations? Does it have to be an exponent of 2?
I'm just thinking out loud here, a point in the right direction would be greatly appreciated.

RS485 is not compatible with RS232 signals. At least you need an RS485 to serial (5V/TTL) converter (RS485 receiver), that converts the RS485 signals into logic signals (Rx) for the FT232. Then try again with various baudrates.

Eventually the brain doesn't use a serial protocol, it may be SPI as well, with two RS485 connections for clk and data.

Wikipedia says DMX512 is 256kbps.

As far as I know, there is no standard DMX language. Different lights have different commands - Some change colors, some move, some have gobos, etc. [u]Here[/u] is a user manual for a random DMX light I found online. It lists the channel numbers and the codes for various functions.