Both of these methods will work very well for small sized organizations or where you need a simple mechanism to create services. For larger organizations or for infrastructure that may be changing rapidly, I recommend fully automating this entire process. I've got a handy little script you can use to do this via a rule.
That's it! What will then happen is once a day this rule will look at the attributes and create a DMC for each of the different values. From there the DMC will constantly look for any new VMs or changes and move VMs around based on the value of that attribute.