I thought about that, I really did. Even downloaded the template to see how much bleed I would need. I've considered it hard, but I would prefer the tag to be in the card and not a sticker the back. I may resort to this though. I wonder if there's a way to get NFC tags on a sheet of paper so I can print the Amiibo logo on them...
You use a foam brush rather than a bristle brush. Comes out pretty smooth.
They're cheap because they're direct from the manufacturer mostly and the shipping from China is about 30-40 days. Beware the ones that say Inkjet printable, contact the seller ahead of time with your printer model to be sure they'll print before you buy then, so that if they end up being the wrong type you can quote their assurance to your printer model and have a no-contest return.