I real feel for you op! My dd went through this at eight and at nearly 11 yrs, is now much improved but we still have issues over procrastination and bathing.
I agree about handing over the responsibility. Found the best way to handle it was to make up a task chart/table which was divided in to two sections: (1st) from after school until bed-time (2nd) waking up until school starts. So first section includes, among other things, doing hwk, signing of hwk book, packing bag for next day, laying out uniform for next day, checking timetable for next day and finding appropriate stuff ie gym bag, music case etc etc. Second section : getting up, brkfast, teeth, ready by a certain time etc etc. It has to be detailed but only focus on the really vital stuff. (Chart was discussed and agreed upon by dd before being finally drawn up.)
A chart is good because you can just point to it, no nagging required!!
And I like Rooble's idea of two lists so the dc can see us doing our bit of the 'contract' too!
Natural consequences are always best ie if gym bag not ready on time we are leaving anyway without it and if you get in to trouble at school that's tough.
I also think its important to continually emphasise the rewards of getting ready quickly ie if we leave on time today with no shouting, I can buy you a treat for break on the way to school or we will go to the park after school (and always stick to your promise). Continually emphasise the fun stuff that comes once the boring stuff is out of the way.
We still have lapses during times of pressure and it isn't perfect but it's better. I really sympathise with the shouting though. I do it (having asked nicely four or five times and been ignored) and I hate it too and wish there was a better way. (I've even included a 'was there shouting?' section in the chart!)
I'm thinking that rewards for good behaviour might reinforce the whole thing (whole chart done properly for a week) or meaningful (to her) consequences if not (rationing of screen time?).
We've just broken up for the holidays so obviously whole term time chart thing will have to be reviewed but I still want her getting dressed and washed at a reasonable hour and helping out in the house. Going to draw up a 'basic contract' with her at the start of the holidays - something we agree together - and will (hopefully) come up with a workable agreement.
Are there any other pressures going on in her life atm? I only ask because looking back, dd was going through a bit of a tough time academically and friend-ship wise at school when her behaviour was at its worst.
Good luck with it all!