I use a form of chipping technique on my Maschinen Krieger builds.
I use a good enamel as a primer, Army Painter matte black. It adheres well and cures rock-hard.
Then I use water-based acrylic finish colors over the primer.
To chip, I use ScotchBrite pads to scuff and scrape through the acrylic to the enamel below. It doesn't take a lot of force to do the scuffing and chipping.
Here's an example from a build I did a few years ago...
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