I got four of these IKEA Frosta stools stacked in my kitchen. I bought them about 10 years ago and they've starting to lose their lacquer finish.
I used sandpaper to get rid of old lacquer and then wiped the stools clean with a damp cloth. 2 coats of paint and voila! There's probably more "professional" way of doing this, but if I get few extra years for my stools like this, I'm content.
To avoid washing the paint tray later, I covered it with plastic bag. I used a small brush for the edges of the stool and a small roller for the top part.
I didn't want to paint the legs, so I used some tape to protect them.
Alvar Aalto designed very similar stool already 1930's ( stool number 60 ), it's now available in different colors, also in turquoise, sweet!