Quick Method for Deepening Crevices?

Hi all, I have a velociraptor head that I've been tweaking in Meshmixer. I've had a test piece printed and found I need to scales to be more pronounced; the cracks between the scales aren't deep enough. Is there a quick method to select all the low points of a model and extrude them? Selecting them all manually will take absolutely forever given the number of scales. I'm using Meshmixer but willing to hear of any other program that could do the job. Thanks!