Here are some ideas that others have shared in books, magazines, and online, etc that have helped them. Please never replace any information for your doctors care for your personal health issues.
For congestion relief, due to colds, flu and bronchitis, try this. You can make a tea or a syrup from hyssop. It can be used as a gargle for sore throat to reduce inflammation.
Externally, you can make a poultice of the leaves and it can aid in healing cuts and bruises. Some have said it helps with the herpes virus. A compress soaked in hyssop tea is applied to sores.
The parts used are the leaves.