Art, you will find that the Vinegar is needed after cleaning with dish soap. The vinegar does remove it if added to hot rinse water.
The above link is an article Mr Smith from England did for us several years ago. He is a master at dying hackle and seal.
Even though finding Veniards might be hard and maybe a bit pricey, does work far better than Rit or Kool aid.
I have had very good experience with using Veniards.