I think the general consensus the other day was about 1 bucket for the whole bed... Slosh it about on the bed... Try to spread it around s bit if you can, leave to soak and then fluff up... This will leave you with a load of pellets forming the bottom layer which will break down over the next few days.
I slit the bag open and pour in half a bucket leave to soak then spread OR bank them up spray liberally and leave then drag down as needed. Great things love them.