Well, as some of you have found out by looking at the more complicated examples, I haven't spilled every secret yet.
Lets do some more stuff with masks.
The last time I used a plain black mask and shrunk it slightly to steal only the clean insides of an area and that's certainly a staple technique that can yield extremely clean edges. But there are a number of extensions to the theme. I will not build a whole texture thing from scratch here this time and concentrate on a variety of examples without necessarily making you follow them step by step. We'll cover Difference and cleaning thin lines and other goodies as we go. It happens when a feathered selection meets with a constant operation at some angle.