HELP! How to get rust of my garden windmill? It's about 4; tall'

Sand and paint with metal paint

Rub WD 40 on the rust spots

Get a product called Bar Keepers Friend. Grocery stores/hardware usually carry it. Excellent for rust. Under $4. It's in a container like Comet.

For a less energetic solution, since its outside and there may be a lot of rust, you can use a product called Naval Jelly available at home stores. It is caustic, so use thick rubber gloves and a paint brush you don't intend to keep. Once the jelly has 'eaten' through all the rust, you can rinse it off and once it's dry the structure will be ready for a thorough coating of Rustoleum.