I think voting with your wallet can be effective on smaller levels: in local communities where reputation matters, in a market where there are enough competitors (not monopolies), when the thing you are “voting” against is the only/major source of revenue, or when the demands are very specific. If anyone has an example of this strategy working on a large scale, I’d be curious to hear it.
Like you said, the organization you are boycotting has to be aware of why it is happening and what is the change that is being demanded. Then, a large enough number of people have to participate to make an impact, which can be hard to do when there aren’t many ethical alternatives. Many people aren’t aware just how many “smaller” companies are owned by the same handful of large corporations, the alternatives are expensive or inaccessible, or they simply don’t care enough to inconvenience themselves.
In some cases the owners of the boycotted organization have their roots deep enough in other institutions (government contracts, workplaces, schools) that they don’t depend on the average consumer.
With enough cocaine usage, you can tear down the partition wall and have yourself a uninostril (not recommended).