I used a kirby grip for the polka dots, and the tip of my white nail art pen from Claire's to do the black stripes and lettering. I really need to buy some proper brushes or something, as I am just chucking away kirby grips (being too lazy to clean them). Bad.
The tips were done by hand, and are (reasonably) straight and even! They were REALLY easy to do - the only tricky thing was trying to write on my right thumb with a shaky left hand, but I got there in the end.
I am smug with nail success.