First of all you should lightly blow on your applicator brush so that if there is any excess blush that should vanish and you do not get an uneven application.
In second step, you should apply blush on apple of your cheek and then watchfully blend it towards your natural hairline.
If you want to apply two shades, then at first apply the darker shade on apple of your cheek and then use the lighter shade to highlight. Make sure to blend them nicely so that there is no visible line between the colors.
In fourth step, you should highlight your forehead, chin and temples.