Here guys dip rusted parts in citron acid/water 10% mixture. Leave the part in mixture overnight, if not clean let it bath little longer. Heat speeds reagtion up.
Wash the acid away with much water and blow dry with airgun. Paint straight away.
If you have a part that you cant dip, you can shop some wallpaper powder and when mixing acid add powder to it. It turns out sticky lime what you can add to your part with a paint brush.
You can get citron acid from hardware/agri shop, pigs need it for some reason.
That acid is enviroment friendly too, so no worries with that.
I remember KapteeniKosmos had some pictures about using CA, in here c-c.com.
Myself Im dipping my doors, only way to get all rust out inside the door.