Hi Jeff and Martin,
Thank you both! For the cleaning of the blade I used a rust rubber gum and at places where it was hard and encrusted rust I used a stone. No power tools involved!
I have used cold pressed linseed oil for years for wood, horn and other natural materials.
Attached are two pictures from "Senjata Pusaka Bugis" of a very similar sword.
Regards,
Detlef