Here is a quick guide to toning in Clip Studio Paint Pro! The tools take some time to get used to, but I suggest that you all try each one of the functions on Clip Studio just to get a feel for what you prefer. This is an extremely basic overview on how toning works, and it doesn't account for print/resizing.
Step 1: Layers
Layers and layer effects are vital for toning in clip studio paint. Here's a quick sketch I made on a new layer above my base layer. If you look on the right, you can see the details and breakdown of each layer and its effects. When I don't know what an icon means on clip studio, I just hover over it and it'll tell you what each tool is used for.
Step 2: Coloring
I usually use colored layers to help me map out my tones easier, and mostly for organizational purposes. Usually I use red for my base color. Don't worry, when the tone effects are added, the red will automatically be converted to black and white.
NOTE: I like to add a little bleed while coloring as well, to make it look more like a traditional comic style of toning. Take a look at comic artists such as Carl Barks to see examples of this.
Step 3: Toning Box
This boxed area is where you can use toning while using masks.Make sure you're on the layer that you want the toning effects to be used on. The little g-pen icon next to the eyeball on the layers show you which layer your effects are being used on.
Step 4: Toning Options
Once you click the tones, it creates a mask so that it only tones the area in which you've colored. You can adjust the number of tone lines, density, and dot settings, as well as the expression color. I personally mostly adjust just the number of tone lines and dot settings to keep it simple.
Step 5: Opacity
I like to adjust the opacity for my tones, so that its easier to read the drawing when multiple tone layers are being used, or you just can't see the line art well.
Step 6: Done
That's pretty much the basics! Always save the original file so that you can make changes later on, and save the web copy in .png format to keep the image crisp. Good luck!