To cook these oils.

As for cure using water, decoctions, of spirit infusions, but a most often are benefit oily remedies ,as of herbs in oil.
Birch.
One glass of birch buds in 400 gr of salt free butter oil mixing, in hot oven keeps for ten hours, filter, cold keeping.
In bronchitis, lungs inflamed ads one glass of oil in one tbl.sp. one of spirit, rub in breast,spine, warm wrapping with scarf or blanket for 4 hours,stay at home, till stopping cough.

In joint rheumatism ads glass of warm oil in one tbl.sp. of camphor, mix,rub in joints for night, after warm same.