(This step is optional. I often do a gradient without a base color)
I sometimes follow this step and sometimes I don't. It really depends on the opacity and color of your second nail polish color (black versus a pale pink). I apply polish from the brush directly onto the tips because I need the strongest color there. If you're dabbing it on, it takes longer to achieve that if the color is light. If you want to skip this step, you can just apply the polish with the sponge more times at the top.
I found that tearing off a corner of the sponge and creating a curved surface can help with the application. I apply the color to the whole of the curve for first application and then when I'm doing touch ups, apply it only on the outside edge,
Repeat this step as many times as necessary.
When I'm doing a gradient without a base color, I'll do a half coat of glitter on the tip and then a second, light coat of glitter from around 1/3 from the base of my nail to the tip so the glitter is denser at the tip.
with a base color
without a base color
Here are my most commonly used nail polishes for the gradients that I do -
OPI "Teenage Dream" is my most favorite glitter polish of all time. I love the slightly pink base and how the glitter shines. I have 3 or 4 bottles of it. As I use each bottle, the polish/formula gets thicker (less polish, more glitter), so I use a different bottle depending on how much glitter I want applied for the design.
If you want to know where I buy my nail deco items, click here.
I posted this tutorial on tumblr awhile ago because someone asked me about it, but I had a really hard time taking the close up photos of my own hands for some reason (probably because I was trying to get the camera to shoot at a downward angle without a tripod wtf).