How to make the effect of "rise" and "descent" with the basses?

[FireSpirit]

Hello guys!

I was learning this hymn, and I thought of "filling the time" in this measure with a "rise" and "descent" with the basses. The chord in this measure is Bb and I need to fall into Bb again. How do I do that? I have attached an example that I saw on a sheet.
I think of making the "rise" on the red arrow and the "descent" on the blue arrow.

 

[Tom]

For the "rise", try playing quarter notes, starting 3 scale steps below Bb: F, G, A.

For the "descent," try starting 3 scale steps above Bb: Eb, D, C.

Or try mixing in chromatics, ie C#, C, B on the "descent". Mix and match and experiment until you find something you like.

 

[Dingo40]

Fire Spirit,
Utilising the bass and counterbase button rows, use the arpeggio of the keys you're in?
So, If in the key of Cmajor, C, E, G ??
( fingers 3,4,2)
Actually, I see the notes are already indicated in the score: those underlined are from the counterbase row.
In the blue box, you've got G,F,E,D
The fingering could be: 2,4, 3 ,2 ??
In the red box, C,D,E,F.
Fingering: 3,2,3,4 ??
Use a fingering that suits you!?
The fingering you use will take a while to get used to ?