Although I've used un-cured putty for belting (still do on occasion, situation determines the choice, as agreed), my current favorite (favorites do tend to be transitory) is cutting strips from flattened and cured GS. This stuff is great in this application as it is very flexible, even on the wider surface, and follows nicely a figures curves, and it keeps 'forever' in the cured state. I've never really liked lead foil or plastic strip for this application-though I've used both-probably because neither material seems to like me much in this way either (mostly as a brother I’ve been told). Besides cross eyed nights of consuming the contents of the primary source of lead foil aren't necessary with the GS method, I most often get my eyes crossed, now, sculpting instead.
Often I'll use the GS strips as a guide to placement and uniformity of width, rather than as the finished piece. The GS is applied (as alluded to earlier) and later, usually when all the surrounding work is done, the final finish/form of the belting is then sculpted on with fresh putty. Of course in the smaller scale I've been working with mostly very little of this is necessary and the GS strip is fine as a finish.
Ray