I had to cut into my pool deck to repair underground plumbing. The opening is 16"x16"x 10 feet. If I mix this in a wheelbarrow I can only do 2 bags at a time and the job calls for 13 bags of fiber reinforced ready mix. Do I do the entire 10 feet and keep mixing and pouring until it's full or should I concentrate on half at a time? I'm not sure I can even hand mix and pour and trowel 6 bags in 30 minutes. Thanks.