I could do it with 2 and merge the bottom 2 layers, or just get rid of the top layer and erase the solid colour.. but I like having redundant layers all over the place in case I want to go back and change something, or just do something in a way that's more comfortable (in this case, erasing the base colours to let the shading through rather than the other way around) It's not really organized but it fits my back-and-forth thought process.
It does seem a bit convoluted. I know a lot of artists who paint their shadows on a separate layer (usually starting from a tonal study), but if you're using brown or purple for the job, you should really change the layer blending mode to Multiply or Overlay so that the shadows blend in with the base colour rather than being a transparent sheet. Leaving it on Normal mode tends to give you a very washed-out look and it works poorly for dark base colours. If the mysterious stranger's cloak was any darker, your shadows layer would actually make his clothes become lighter because the shade of brown you used would be brighter than the cloak. Do you see the problem?
Secondly, you don't need two layers for the base colour. If you're worried about making a mistake that you won't be able to correct later, you could always use layer masks to paint in the shadows. It's the third icon at the bottom of the layers palette. A layer mask will hide certain parts of a layer, so you can decide where you want your shadows to appear. This is what's called non-destructive editing, because you can always undo the change later. Watch this video for a quick tutorial:
Lastly, if you don't know about layer masks, which is a fairly common process in Photoshop, it leads me to believe you're not particularly savvy with the application. When you have time in between chapters, you should check out a few tutorials on YouTube to familiarise yourself with Photoshop's different functions. It will help you save time and the comic will look better too.













