show only unique values within the multi-select dashboard but filter by contains any?

Hi All,

We currently use a Multi-select picklist to store our marketing opt out values in CRMOD under the Contact object. I have Combined Analysis reports that takes the whole or a portion of our customer base and subtracts any of those that have selected to opt out of particular comms, (through the use of dashboard prompts). The end result is we have a mailing list to upload into our 3rd party Email Marketing tool.

So, I guess I have two questions, one about the current set-up and the second about if this is the optimum way of managing opt outs in CRMOD.