I had those exact chairs and painted them last year. I found it's right pain in the chuff to get properly in between the slats on the back rest and underneath bits but once it was done they did come up lovely!
I was as happy as a pig in shit painting them to be honest. Tunes on, sun beating down, the only spanner in the works was the paint ran out so the underside is a bit half cooked, but fuck it, they'll do. I'm not planning on having the Queen around for tea anytime soon!
They do look good when they are done. I like a bit of garden work when you can just blast the tunes and get in with it!