Games : How to cycle through the various units/buildings in a single control group?

I usually assign all of my command centers to hotkey 4. Let's say I have three command centers hotkeyed. Double tapping 4 would take me to the CC which I selected last when creating the hotkey assignment. Are there any tricks/tips for quickly cycling through all CCs (i.e., centering the screen on the first CC, then the second CC, then the third CC)?

For example, right now, I am doing the following to change rally point for each CC (to a different location): press 4 to select all CCs, click on the first CC in the green wire-mesh list of selected units, do the hotkey for centering screen on selected unit (Ctrl+F in my setup), right click to assign rally point, then repeat for all CCs. I figured there is probably a more efficient way.

Or do folks simply assign each CC to a different hotkey? (I currently assign to just one hotkey because I'm already using six other hotkey assignments).

I'm using CCs as an example - it would be helpful to understand how to do this for any given group of units/buildings.