Flow is not that hard to achieve.
I really don't put any effort on it. You just have to make everything pointing at your focal.
I mean, the focal must be brighter and more sharpened than the background and of course, it should attract your eye's attention in first place.
However, if you really want to work on the flow, then you have to come up with things like the brushes voqus mentioned or something else that would improve the space that surrounds your focal point.
About the effects, you just have to change the mode to lighten/color dodge/screen/linear dodge and so on :D