Gridding (my thoughts)
I have gridded some of my Teresa Wentzler wips, and have found, especially with Storyteller, it helps TREMENDOUSLY, especially where there are all of those 1/4 stitches in the wings.
When I do grid (which isn't as often as I'd like, because I jump into new things often - I just can't stop myself, lol), I like to use a nylon filament. I haven't tried some of the other fibers that I've seen recommended - I just had some nylon thread on hand. The kind I use comes in both black (really dark gray), which I use on lighter fabrics, and clear. The thread doesn't split, and is fairly easy to remove once I've stitched the area.
It was easiest for me to grid every 10 stitches, and I match my gridlines to the gridlines of the chart - makes it much easier to reference the area I'm stitching, and figure out what stitch(es) I might have missed. If you look at Storyteller closeup (below), you'll see what the gridding looks like.