While playing hymns, you will need to harmonize. It is very necessary. Sompe people find it difficult to play a particular note with one hand and another note on the other hand. This technique will really help you if you listen.
We shall be using the key of C# for an illustration.
The trick is you will be playing chords with the left hand and the right hand will be playing the note of the hymns. You would not need to look at your left hand while it is playing the chords. You would only have to focus on your right hand that is playing the notes.
So in order not to be able to look at the hand playing the chords you must find a way to play them without moving your hand too far. Look at the illustration below o the key of C#
C - G C E ----- Middle finger - Pointer - Thumb
F - A C F ---- Middle finger - pointer - Thumb
G - G B D ---- Middle finger - pointer - Thumb
A - A C E ---- Middle finger - pointer - Thumb
E - G B E ---- Middle finger - pointer - Thumb
D - F A D ----Middle finger - pointer - Thumb
B - you can use the chord for G to play it.
If you can master them perfectly, it would be easy for you to play hymns, it would also be an added advantage for you when playing other songs.