Cluster thinning

Now that we're almost through veraison, It's time to remove those clusters that haven't turned completely black. We're having some trouble finding laborers to do the work, since other parts of wine country are in the thick of harvest. I'm reluctant to just hire guys off the street, because of the decision of which clusters to remove. I'd rather have workers who are familiar with the work when the quality and quantity of the final product is dependent upon the choices that they make. But timing is important: the less-ripe clusters will be impossible to distinguish from those that are good when the color is more uniform.
I may be forced to hire workers off the street, and do their training on the job. Yikes!