/ic/ - Artwork/Critique

I've been studying some doujins from pija and I have a few questions in regards to pic related.
For sample #1 I see these dots close up on the skin of characters, what it their purpose? Is this done when rendering?
For sample 2 he uses a similay texturing effect for backgrounds, is this done using a specifc brush?
For sample 3, pija always add shading to the privates of his female characters, however I see that it's somehow layered and linear, did he just use an airbrush and vertical lines for this?