I have used diagonals on just about all the baby quilts I make. I use my Omnigrid yardstick to make the lines 1 1/2 inches wide. My favorite marker is the blue washable marker. I always make test marks on all the fabrics used in the quilt before I start piecing. Then when I am ready to mark, I get the test marks wet with cold water to double check they will come out. I have ironed over them and the marks still come out, but I wouldn't recommend this as the directions say not to. Anyway, I like to use a converging chevron pattern, so that begining X gets filled in on all sides with diagonals. I use my walking foot to follow the marked lines. After it is bound, I agitate the quilt in cold water, spin that out, then wash with warm. Into the dryer and it is done.