How do you feel when clefs change in the middle of your organ piece?
A lot of my students get confused. They stumble, they slow down, they even miss the change and continue to play as if nothing happened.
What can you do to speed up your clef reading?
For starters, practice parts with a more challenging clef twice as much.
You see, one clef takes about one month of focused practice to get more comfortable.
If you find it difficult to read the bass clef, devote just one month to exercises with this clef.
It will feel like hell at first but it gets easier with time.
If you want even more challenge, take a right hand of your organ piece and transpose it to the bass clef.
Organists should feel at ease with both the treble and the bass clefs.
If you insist upon it for some time, you'll find a lot of things that are much more challenging than changing clefs.