Consider cross hatching. I do it using a line of blue painter's tape. I lay the tap across the quilt and sew with the edge of my foot against the tape. Dom't try to sew right against the tape as you might catch the tape with your stitching and then you'll have to get the tape out of the seam. Sew up and then down the other side of the tape. Then move the tape over, line it up on the quilted line and sew down the other side. When the tape loses its "sticky" get a new piece. When you have finished in one direction tape across the other way and sew again.