1 - Rinse using hose to remove the bulk of the dirt.
2 - Use warm soapy water and work from the top down using a sponge to apply.
3 - Rinse with clean water until all soap suds are gone.
4: Rinse using hose to remove the bulk of the dirt.
5: Regularly applying wax to your gate/fencing will make the gate/fencing much easier to clean next time around, as well giving it more protection against the el-ements.
Things to look for:
When cleaning your gates/fencing check for scratches and paint chips. If you find any areas, you must treat with anti-rust paint. Leaving the exposed area would mean it will only get worse. Catching the problem early would stop the rusting and solve the issue.