After looking at the scans, it looks to me like the desired effect may be a "slide" to open or closed hat on the note following the -. I say this because some of the -'s are over rests. As Wilmer said, that would indicate leaving the hat in the previous position indicated, and then reversing the effect on that note. So, + - 0 would be "Duuuwwwah" (or something like that
), instead of Du Wah. Clear as mud, right?