gb,
Before you start, contact `Health & Safety` for advice, tell them what you are going to do! its best to find out if you will need to comply with any new legislation etc.
You will need to make a assessment of the area, i.e
what standard of cleaning do they require? what machinery can i cover with sheeting? is this safe- given machinary maybe hot due a production run etc.
Access? will people be working beneath me? etc.
Use cloth dust sheets where possible (they absorb dust better than plastic covers), and if possilble try and hire a back-pack vacumm cleaner for the awkward bits!
When you are vacumming, you will knock dust everywhere when you don`t want too! (this is normal, and can`t be helped)
I would also consider hiring a industrial air extractor connected to a pipe to the outside, this will catch the bits of dust etc that has fallen.