It all depends on what you are trying to accomplish, but the manual is the starting point. Custom controls are a step sheet of instructions to perform repetitive actions precisely every time. What I generally have people do is write down what they want, and then write down the physical steps required in the custom control to complete and build the customs accordingly. Say you have a monitor you need to feed with a server clip from a clip list in the switcher.
The actions might be:
Cue the clip number from the clip list (would be fount under vtr/server control)
Select the source on the aux bus (might be bus source select in Caprica, or simply punching the source on your aux bus in Vision/Acuity)
Play. (back to server/vtr commands, locate the channel, and select play.
Or it could be something a bit more intensive. Custom controls are very capable, but it helps to have a goal, so you know what to expect when completed.
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