There are far more complicated ways of creating a glow or a smoke effect, but I've been trying to find the simplest way of doing things and I think this is a simple but affective method.
I'm sorry that the pixel fairy looks absolutely terrible, I had to redo her entire section because the first time I drew her normal size and then resized the drawing so she was easier to see but it went horribly horrible wrong and didn't look right. So instead I drew her about three times the size she should be which made it better looking for the purposes of the tutorial but she still looks a little off, can't win.
Night Sky tutorial: [link]
Cloud tutorial: [link]