If I want to flush out my Power Steering Fluid, about how much does it take to refill (TJ) ?

Why flush? Do you suspect a source of contamination?

Just drain - undo the lowest point I guess.
Refill - manual warns against starting the engine as air is absorbed into the fluid and makes the pump make all 'orrible noises. You are supposed to disable the ignition and
crank the engine over without it firing. Keep topping up until the level no longer drops.
It takes a while.
Shouldn't really need to do this unless you have replaced the steering rack or such.

To answer your question, 1 L from the dealer should do it.

You should "flush it" with new fluid.

E.g.
Drain old fluid
Top up
Start car and turn steering from left to right to flow fluid through system
Drain
Top up
Done

But yeah 1l will be enough.

Is flushing necessary? Is it mentioned in any service manual?

But yeah 1l will be enough.

Tanks

Yeah if you want to avoid changing power steering pumps it is.

When you change fluid, the fluid you're taking out is quite dark compared to the new stuff. What you can remove from the reservoir is only a small amount, theres still lots of burnt PS fluid in the rest of the system (E.g. PS fluid lines, rack etc).

No its not strictly necessary nor is it mentioned in the service manual, but its good to do.

Good point.