How to get Barielle nail polishes for $3.75 each (or less) with free shipping today and tomorrow (April 10-11) only

Disclosure: This post contains affiliate links.
They have some crazy-awesome colors available, like Falling Star (blue with copper glitter) and Myrza's Meadow (pale lime green with fine holographic glitter). Google "Barielle swatches" to find lots of other ones. I strongly suggest googling anything you see on their website that intrigues you, because their own computer-generated illustrations of the colors are sometimes really inaccurate.

Here's how you get them for $3.75 each:

1. Sign up for the mailing list using the link that says "Register and receive 15% off". Wait for an email with the discount code (should only take a few minutes). 
2. Add an even number of nail polishes to your cart, because they are all BOGO 50% off.
3. Enter your email code to get 15% off. 30% off PLUS free shipping will be added automatically when you check out. After all that, each bottle will be just under $3.75.
4. If you decide that there is a kit in which you really want all 5 polishes, they will end up being $3.50 per bottle with the 30% off discount. The BOGO 50% off deal doesn't apply to kits. The new Sweet Treats Kit looks particularly cool - and the Blue Cotton Candy polish included in it looks like a dupe of one of my favorite Butter Londons: Victoriana. You can also buy Blue Cotton Candy and the others as individual bottles.