hii, i guess this wont be a straightforward answer as well, but i hope it'll help.
if you are still breastfeeding her fully, you will need to take one feed off gradually, and replacing it with the bottle, example, stop breastfeeding her for her morning feed, and you will have to bear the pain a little bit, only if it becomes unbearable then, you could express ONLY until its comfortable again, the reason being when the breast is not cleared out, your body will think that the milk is not needed, so in a day or two, it will stop producing milk for that time slot. (does this make sense?)
So it will take a while for both breast to be totally dry out, depending on how much milk your breast is producing now. I weaned my firstborn at 8 months, and it took about 2 weeks, then you'll be left with very small amount of milk.
For the pain, express only as much as you need to, or panadol.
good luck
mum to Keenan dec 2002and Lilyan jan 2005