I love a good eyeshadow primer, this is a must if you like to apply your eyeshadow and make sure it stays on all day without creasing. There are many eyeshadow primers around, I once tried the ELF one but found it to be rubbish. My must have eyeshadow primer is the NARS Smudge Proof Eyeshadow Base. Eyeshadow primers I find are something you do have to spend a bit of money on.
Urban Decay do a few different eyeshadow primers and the one I like using is their original Eyeshadow Primer Potion. It comes in a nice squeezy purple tube along with an applicator. The squeezy design is really good, when you need more to come out all you need to do is squeeze the tube. The applicator has improved since I tried this many years ago. Before it used to be a slanted doe foot applicator which I really didn't like. Now it's just looks like a normal shaped one.
To use on the eyes I just paint a small amount on the eyes. You don't really have to wait for it to dry either, you can just go ahead and apply your eyeshadow. It definitely keeps your eyeshadow on all day and it didn't crease once. So it's a pretty good product.
I like to use this under my eyes too. I do tend to get fine lines under my eyes which means when I apply concealer there it makes it crease like mad. I did try the Smashbox Under Eye Primer, but for some reason it's just stopped working. I tried using the Primer Potion under my eyes and it does a really good job of stopping my concealer creasing. I just apply a small amount under my eyes and then apply my concealer on top. You do have to be quite quick with the concealer as the primer does tend to dry fast.
Overall i'm really happy with this primer. I got this for £16.00 in John Lewis.