I believe there's some sort of preparation emery board that you can get to make application of these a lot easier. If I'd thought about it before I started applying it, I would have used my Nfu Oh Aqua Base but I completely forgot I had it until just this second.
Layla is an Italian brand. In the UK, it can be purchased from Sally Magpies (which is where I got mine from. Check out their FB page for specials and sales). In the US, it can be purchased in store at Ulta. If you want to support independent companies, it can be purchased at Ninja Polish, which also ships worldwide.