If you are machine quilting, then it will be jsut as easy to do diagonal lines all across the quilt in bothe directions. I use masking tape to mark stitching lines instead of a pencil. Just take care not to let your stitches drift onto the tape, makes it harder to get off afterwards. Going diagonal through all the blocks won't be as much trouble as stopping and startin to only do certain ones, if you are machine quilting, that is. Low loft batting should work just fine , that way you can still move under it instead of being weighted down with a thicker batting. Good Luck!