So I went a little nutty and made an image to illustrate how I do the gradient. J's always saying how well I do them, but it's probably just that I have time on my hands (no pun intended) so I can patiently do the gradient.
It's basically this:
1) Paint horizontally a thin layer of polish about 2mm wide starting at the tip of your nail & let it dry...
2) Paint horizontally a thin layer of polish about 4mm wide starting at the tip of your nail & let it dry...
3) Paint horizontally a thin layer of polish about 6mm wide starting at the tip of your nail & let it dry...
... you get where I'm going with this.
▪ You can do the width as wide or as narrow as you like.
▪ You can also paint vertically (I do that once in a while - most often on the last coat - the widest one).
▪ You can do more than 3 layers... sometimes it takes 4-5 depending on how translucent the polish is.
▪ I recommend making your layers thinner because the gradient will look more like.. well, a gradient.. instead of clumps of polish :P
But that's it. I only suggest doing the last (top) coat of gradient color as the most space covering coat (5-6mm) because it covers the texture of where the under coats end. Makes it a bit smoother. Gosh, did that make any sense at all? ** update 6.15.2012 ** I believe I've found a better way to apply certain polishes as a gradient. It's a tutorial for Ombre Nails that I found on thebeautydepartment.com. I think this would work great for gradients Here's my post on ombre nails