to practice in/at doing something

[allthewayanime]

If I talk about an activity do I say ' while she practiced in/at doing that job'?

[bhaisahab]

If I talk about an activity do I say ' while she practiced in/at doing that job'?

What exactly are you trying to say?

[allthewayanime]

This is the whole sentence: Aethelflaed wasn't new to this: in fact she had already practiced at/in doing her husband job as the ruler of Mercia before his death.

[bhaisahab]

This is the whole sentence: Aethelflaed wasn't new to this: in fact she had already practiced at/in doing her husband job as the ruler of Mercia before his death.

Where did you find it?

[allthewayanime]

I made it from my history book and I would like to know if I should add a preposition: at or in?

[bhaisahab]

I made it from my history book and I would like to know if I should add a preposition: at or in?

No preposition is required. It's "practised" in BrE by the way.