Here you Chris (and anyone else taking an interest)
I make reins using a standard white paper/thin card (it's about 80gsm) I pre-colour with paint in a block as shown. Ordinary acrylics are fine for this or you can use a Sharpie for black. Then I cut a lot of strips using a scalpel (new blade please) and a straight edge. Most of these won't be used, but it's handy to have a selection of very slightly different widths I've found and these are glued into place using PVA. Once in place and the glue has dried I'll paint/highlight and touch up as required. I've also found with the French Napoleonic bridles and reins that it's much easier to do a couple at a time because it makes painting easier.
Many thanks Paul. Greatly appreciated. I was thinking of using silver foil from the lids of wine bottles, but I think your approach is more practical. The model is coming along very nicely indeed. Look forward to more postings of your progress.
Stay safe over there
Warm regards
Chris