Whether its the best way to do it or not, or the only way im not sure.

Its a bit hard to explain, but ill try with a step by step guide thingy.

1. First select the body part where you want the dial to be. Lets say the head (but it can be anywhere even if its a face morph). Select the head of V4 and then select a category headline where you want the Master dial to be, so for instant "Other". In the top of the screen is a small white arrow, next to the "properties" tab, if you click that, you can choose "Create new master parameter", click that and give it a name, this will create a new Dial, which currently doesn't do anything.

2. When you click ok the "Dependency" menu or what its called will open :) At the top you have two tabs "Keyed dependencies" and "Value operations". You are most likely in the "Value operations" so click on the "Keyed dependencies" tab.

3. Now what you want to do is to tell Poser which dials this new master should control and how much effect it should have. But you do this by "teaching" it. . Next to the "Start teaching button" it will say "0.0000", click that and set it 1. (If you want a more sensitive dial you can set this to 10 for instant, will make more sense in a second :))

Now press the "Start teaching button" and leave the window open, you can drag it out of the way if needed. Go to V4 and change the values to what you want them to be. Be advised that if you have already set them, you have to set them to 0 first and then to the value that you want them. As you do this you can see they pop up in the "dependencies windows". So go through all the dials that you have changed, until all of them appear in the list. Once you are done. Click the "1.000" in the dependencies menu and set it to "0" again. Then you go through the list in the dependency window line by line. When you select one, it will highlight it in the dial menu on the right. Now you set all of them back to 0 one at the time.

4. Click the "Stop teaching" button.

5. Now if you could follow along in this slightly confusing tutorial :D your new dial will now control all of them.