One of the things that irked me the most about shading with layer modes was how annoying it was to change the color after shading. Sure, you could alpha-lock it and airbrush over it or change the hue/saturation in other ways, but I wanted to be able to quickly grab just the areas I'd shaded or do fun funky textures or only affect certain areas.
That's how I got into using masks! I feel like masks get a bad rep in the digital art community because they can be slightly daunting to use, but they're a way to ensure complete editability of your work. Because you're only affecting the transparency of a layer, you can change it, grab it, wonk it, tweak it, bop it, and it all works out in the end!
A couple useful shortcuts:
Ctrl-click a layer to select it. This is good for quickly adding a mask from a selected area like your flats.
I've said it before and I'll say it again, if you use clip make sure to use that alpha-lock and eyedropper tool!
masks can be pulled to other layers, replicated, merged with other masks-- there's so many options here.
These little stencil boys are the bees knees!