Just got a bid for a barn addition approx. 4500 sq ft. all cement block, owner wants 1 coat SW block filler and 2 coats SW Super Paint. I have never used the block filler. Did read up on it a little says 50 to 80 sq. ft. to a gallon and takes a .021 to .028 tip to spray. My question is has anyone used this and have any tips or things to watch out for.