My name is Merrill Fox, and I'm a pressure washer distributor in the USA. Before, I had a contract cleaning business and have cleaned many grease hoods.
First of all you need to make sure that there is a working drain, and invest in a wet vac and maybe a puddle pump. This is for water control.
Secondly, to clean the hood and filters is one thing., another is the duct that rises to the roof with the air mover on top of it.
You will need a hot water pressure cleaner.
Start by removing the air mover fan and you can use wand extentions or a telescoping pole to clean the grease. You will need a heavy duty degreaser with plenty of potasium Hydroxide in it. ( caustic )
I would reccomend a plastic sheeting be placed over the stoves and remove the grease filters. You can then wash from the roof down and wash the hood and filters.
This should be done on a periodic basis. You will need to manage the water and clean up before putting everything together. If they want the entire kitchen cleaned in addition, you will need to first pull all of the debris out from under the whole kitchen line. Then you need to be concerned about the electric. ( shock hazard ) I would shut off all elecric to where you are cleaning and wrap all electrical boxes and fixtures to protect from the moisture. Again water management is critical. You may need some helpers with some floor squeeqees..
This is a messy job and will have to be done usually at night.
You can look at pressure cleaning eqipment at
www.merrillfoxenterprises.comGood luck,
Merrill