1. Do not lift the fingers off the keyboards. Loosing the contact with the keys will greatly diminish your ability to control the releases.
2. Legato touch is not useful in early music. Consider playing with articulate legato even in the middle voices.
3. Avoid very short staccato touch. Extremely short notes can be used effectively on the piano in fast tempo and lively character pieces but on the organ, make the notes longer.
4. Play the organ mezzo piano. Avoid making dynamics with your touch. Instead use as little force as possible.
These things require great attention to detail and focus, otherwise it's easy to get back into habit of playing the organ with pianistic approach. However, if you listen to the result of your organ playing, you will understand why it is better to learn to play the organ differently. By the way, the same points are valid when you practice organ pieces on the piano.