Use engine degreasers and rags at first ,if you must washing the engine then use a proper product ,you may use turtle's presoak ,spray it with air pressure on a dirty engine ,agitate the rust with brushes of different sizes and kinds,you may use proper detailing brushes .
Caution !
Keep your hands gloved when using presoak as it is acidic .
You need be careful ,don't soak injector wiring and other sensors ,better wash at home and use tumbler instead of hose of water.