This map is pretty rocken Quabbe. Keep em coming man.
And for the technique: I forgot to mention that I put the opacity of the brush to 45%.
I often use this technique of contracting or expanding a selection and stroke it (with or without pathes). It is very helpful and comfortable to use automated actions for that (window -> actions). Just safe the first few steps as action, put on play, lean back and watch the machine doing your job.