I learned a lot from tutorials on DPW, like: http://www.dailypaintworks.com/ArtTutorials/ArtByteSummary/30
and youtube vids. For me, it resulted in a taking of a little of this and a little of that you see that you like and incorporate, keep painting and develop your own way. And since to me a good painting is varying edges, and mixing a little color of each area in to the others, it is becoming for me a bit more instinctive. Because I have learned what I like and consider to be successful, some of these things I don't have to think about as much.
I do think some varying edges contribute to looser style of painting. For me, my work became a bit looser after my confidence built up a bit and I became freer with my strokes, using less due to knowing where I wanted them and the color to go... Certainly, hyper-realistic painters are not loose. People make a big deal about it, but it's just fun to experiment and develop your own style. To me, I think looser is letting the brush work for you (becoming one with the brush, haha), and mixing colors are a bit more freely. Less brushstrokes, instead of 'over-painting' areas. Well, yeah. I'm not doing any better describing loose vs tight. Sorry!