Lena1952 -- if you have it available on your sewing machine, sounds like your grid quilting idea might be perfect for the serpentine stitch, that is sort of a multistitch zig zag. Basically you point the direction and your machine will do the work for you. The wavy line is more forgiving to both staying where you want and if your piecing has a few irregularities. Close is good enough! I press open and another thing I like about it is both sides of the seam allowance are stitched down.
Some people are able to do the little waves themself, but I lack the regularity for small repeats. Doesn't mean you can do larger repeats, even over several inches, just make sure it looks deliberate
