a hunk of (bees)wax is really good for that – just draw the string through the wax a couple of times and it’ll stifen up (though it will be somewhat sticky).
Well an interesting challenge that harkens back to the sorts of articles one reads in issues of Model Railroader back to the 1930s! People made use of all sorts of stuff back then, even eyelashes. They were modeling on a shoestring so to speak [:-^]
A flat fabric type shoe string, if cut to the right size and somewhat trimmed, could look like a sack of some product – seeds for example. A stack of sacks along a wall.
Covered with glue and then dipped into ground foam a flat fabric shoe string could look like a slightly elevated garden plot. Or a slightly elevated fresh burial plot.
As for the round type, I have need of a product to fill a gap under a bridge between the bridge abutments and the road. I thought I had measured things more precisely but there is a gap. Pressing in a shoe string of the right color might be just the thing (I was thinking of jute twine).
The round type might be the right size and the right flexibility for the hoses that brought water from the tender to the steam locomotive.
I lay the shoe string up against the rail (stretched a little) so it’s right against the rail. I use Rose-Art modeling clay to make the ends of the crossing. This also holds the strings in place. I pour the plaster and let it set. When I take the strings out, viola, flange-ways, quick and easy.
I’m a J-toe boot wearer myself so shoelaces/shoestrings are a rarity around my house; I do have one pair of Sunday-go-to-meetin’ shoes which I bought almost four years ago and the laces in them are showing no sign of weakening.
I do recall, however, a layout which featured shoeSTRINGS running down the side of the building and which were designed to simulate some kind of outside-the-building plumbing. I also seem to recall someone using very short lengths of shoeSTRINGS to simulate splices in a telephone line. I would probably have picked plastic or brass for that sort of fabrication but I guess if you’ve got the shoestrings and can’t use them for anything else and they work then that’s a buck or two in the bank!