I, too, have not graduated to free motion. I do a lot of children's quilts, so they are often brightly colored. I've found that Gutermann invisible thread works well for me when I'm in your situation. It's color #111. I get it at Jo Ann's. (It's made from polyamide and used in most industrial clothing manufacturing.) I use it in the top and regular thread in the bobbin (that blends with the backing). I have a vintage Singer 401 that I mostly use when quilting. I use a walking foot. If you get your tension balanced, the color of the thread for the backing will not show on the front. (Occasionally, I loosen the top tension a bit. I probably don't need to.The first time I tried invisible thread (Coats and Clark), it stretched so bad, it puckered the fabric.)
For how to quilt it, I would do stitch in the ditch or something similar on the horizontal seams. Then I would pick a vertical seam about 5" from the edge lines up and just follow it as close as you can to the bottom. How close you put your quilting lines depends on your batting. I generally use Warm and Natural, so I try to sew a quilting line every 5".
Another option is to do diagonal lines. I've done that before, too. Because your thread is invisible, you won't notice if the line is a little crooked, especially after it's washed. If you kind of "aim" at the next corner, you don't have to mark it. If I feel like I have to mark a line, I use blue painters tape. I don't do it often enough to know which tape sticks best, but there was a thread about it recently. Just don't sew over the tape, it's really hard to remove when you do. Sew next to it.
So that I don't have to tie threads and worry about back-tacking, I sew off the edge of the top and up (or down) to the next row (on the batting).
bkay
