Moving from General Port to Specific

I'm working on cleaning up our BIG_IP box and would like some advise.

A few of our virtual servers were configured using Port 0 (Any) because people didn't bother to figure out what ports would actually be used. No monitors were set up except for "gateway-icmp".

Now I'm trying to change these VSs to use the correct ports and I wanted to be sure that while I cut over, nothing will fall between the cracks.

If I create a VS on a specific port, which one will take precedence? Will the port 0 VS still take all the traffic or will the more specific pool kick in immediately?

Is there a best practice for doing something like this on a live, production system?