I've used handwriting recognition software quite a bit in the past. There are several gestures that would be extremely helpful including line break, undo, redo, delete, and space. For a line break, I've seen a backwards capital L with a long bottom part like _|, started from the top. For undo, I've seen a large greater than sign drawn from the top, and drawn from the bottom as the redo gesture. A simple long line drawn from right to left was used for delete. A squared off U like | was used for a space. With these gestures, I found that I rarely had to move hand from the writing area and the handwriting recognition was much more useful.