how do you set trunk mounted amp gains?

I've set them up before with a amp the is mounted under a front seat. This is easy, I like to have all the doors closed, windows rolled up and trunk or hatch closed. It will be the first time (properly) setting gains on a car that will have the amps mounted in the trunk. If I want to sit in the driver seat and set up everything from there. This looks like a two person job, I would need someone in the trunk turning up the gains slowly. How should I communicate, yell to the person when it is at a good level? Any insight on who the pros/experienced do it?

First find the max safe level by setting it just below the clipping point using the instructions in the Hot Topics forum (and don't forget to wear hearing protection.)  Then, if you want to turn it down from there to blend by ear at normal listening levels, yes you'll need an assistant to adjust while you sit in the driver's seat.Support the12volt.com