It is more like a step by step + some annotations. I am afraid I dont have the vocabulary in english to explain with detail, so I hope it is clear enough
A dear friend asked me to do this, so here it is^^
I draw the mouth very simply, really, it is just 3 lines, basically
The important thing to remember about the mouth, is the curve it has over the head, and the angle of the lips.
And for painting, I usually paint over the skin tone, so it looks more natural, and with a red/brown tone. Not too red, unless they are using lipstick
Always try to keep the volume, the lips are a protuberance and they should feel like that.
The shining effect I do it with the brush in dodge color. I helps to give the lips that sexy look
But with men lips, the effect needs to be more discrete.
I hope this is useful for someone. If you have any question, just ask