"Behind the makeup and behind the smile I am just a girl who wishes for the world." ~Marilyn Monroe
You might be surprised at which part of your eyeshadow application is really the most important.
It doesn't matter if you're only using one color of shadow or a terribly complicated, multi-colored palette- the most important part of the entire process is proper blending. No matter how beautiful a color is or how great it looks on you, it's going to look awful if it's blotchy or uneven. You're better off choosing fewer colors that you blend well than a complex palette if you don't have the time to blend properly. Good blending is the only way to achieve a sophisticated makeup application where colors blend seamlessly into one another and at the outer edges.
For this you need a brush- but NOT the one you've just applied your color with. It should be a clean, dry brush; you can use this brush to blend all your colors- just buff the brush on a piece of tissue or paper towel after using a darker or more intense color to avoid 'muddying' the other colors. When I was in art school I was taught to experiment with brushes and find my own ways to use them. As far as I'm concerned, when it comes to brushes it's the same with makeup as with painting: whatever works for you is the right brush for the job. Most MUA will suggest a 'crease' brush for blending- and I find that works well for me- but if you've not done so before, try out a few different bushes to find what you like.
You can blend after applying each color, or - especially if you have a more neutral/natural palette- you can wait until you have 2 or 3 colors on and then blend. Most of the time just a gentle buffing motion- back and forth, or around in tiny, quick circles, will do the job. Find the motion that works for you. Obviously the more complicated your makeup the more blending required.
If you run into trouble blending a color at the outer edges remember you can always use a translucent powder or foundation powder with your blending brush to make things go more smoothly. You can also 'tone down' a too-heavy application or too-intense color this way, too.
If 'blending' your eyeshadow colors isn't something you've paid a lot of attention to before you're in for a pleasant surprise. You may find you're a makeup artist in the making….