It look me years to figure out how to blend my eye shadow properly. For a long time, I would only use my fingers to apply my makeup. I can say first hand that fingers and eyeshadow generally don’t mix, you need more precision that what the tip of your finger offers!
Firstly, good quality, clean and dry brushes are essential! Bad quality brushes won’t have the same evenly applied look, and can even scratch your skin which is painful. Always test the brush bristles and make sure they’re super soft with no flyway hairs sticking out! This will leaves streaks of eyeshadow around the area that you don’t want. This is especially important when doing more intricate, precise designs. Make sure the bristles are super dense as well. More bristles, the better. Make sure you’re using the right sized brushes too.
Another important thing to remember, is “it’s all in the wrist.” As in, you don’t want to be moving your entire arm to move the brush across your eyelids. I find, leaning the palm of my hand against my cheek and only using my wrist to move the shadow. It’s way steadier and you can be more precise, especially if you have shaky hands.
Lastly, applying a base is going to help your colour distribution and prevent your eyeshadow from looking patchy. The skin naturally is a little uneven, so applying a good, thick consistency concealer will do you eyeshadow wonders.