Try this... I use a brush that is the same as MAC 224 (Sonia Kashuk pointed blending brush).
For a 2 color eye with a separate crease color and a browbone highlight (4 e/s) I will start with the line between the 2 lid colors, moving from the inner eye to the outer eye, ONLY in one direction, and NOT back and forth, this will cause the e/s to become "muddy"
Then I will blend the crease color with the lid color, again usually in one direction only, but for the crease you "can" go back and forth if you want.
Then I will blend the crease with the browbone highlight color, and for this I will use circular motions very lightly and keep going until it is blended. Don't ever try to rush blending or it will come out wrong...