Thank you!

So, for the effect I used Clip Paint Studio. Any brush will work for this.

So, first of all, make your first lair a single darker shade of a color, in this picture, a really dark brown.

Next, create a new blank lair above your shaded lair and draw a straight diagonal line across your whole canvas. Then copy that lair and move it slightly above the first line you drew. Make sure it's not TOO close that they're touching. Then merge those two lairs. You should now have one lair with two lines. Now just repeat the same process until you have so many lines that it covers every part of your character. Once you have that, make sure all the lines are on one blank lair!

The final step, look to your layer bar in CSP. Click the farthest left icon, the one that looks like a dotted box on top of a grey box. This is the "Clip To Layer Below" option. Click on this icon on the lair with the lines.

Now those lines have merged with your shaded lair!

If you still need to change the shading after this, you won't need to worry about doing the lines again as long as that line layer remains above the shading lair!

Hope that helps!