You will need...
Very easyCan't elaborate on that - think of it in a no-news-is-good-news sense. It's also pretty quick if you exclude drying time.
Time20-30 minutes excluding paint and nail polish drying time.
More bargain Binns
Tip: Speed up the drying process by using a hair dryer or heat gun. Craft professionals may recommend the latter but if it's not available or your idea of cash well-spent, the former works perfectly.
Now for your paint design! I chose black, red, orange and yellow but you can try experimenting with other colour combinations. Dunk your nail polish brush as deep into the bottle as possible, so that it's thick with nail polish, and shake it so that drops fall onto your dry puff paint; alternatively, paint it on thickly. Repeat with the rest of your colours and hold your puff paint vertically so that the nail polish runs in painterly lines.
When your nail polish is dry, you can use clear nail varnish or lacquer as a fixative.