Exactly right; that's what I do. I keep a mix of tacks & ties in a small container.

I have seen another variation of this idea that I forgot to mention earlier. Instead of a thumbtack shape, it is a small cube with reflective tape on all but 1 surface; that surface has a small tack-like spike on it. These units can be seen in a 180 degree hemisphere (or better) but still require a clear & solid section of wood for placement:


Holy moly, here is a page with all types of reflective trail markers, including some I hadn't seen before!