On my vintage
coach bags, I have used Angelus leather paint after all conditioning is done so the edges are hydrated and not too rough. Sometimes a gentle nail file maybe needed to smooth a rough spot out. I tried to fix actual edge coat on a very small
Fendi peekaboo monster I got dirt cheap and a Celine nano to mixed results. The
Fendi came out beautifully, the Celine was a mess although the previous owner had already done and removed whatever they had done before I got it. So I cannot say if the problem there was my application, the product or just that the strap had had too much done to it.
I forget the product I used, I did post about it in this thread, but it’s more readily available in Europe and I had a tough time getting it in the US. I bought the matte version because it was all I could get, but there was a glossy version and a substance to make matte glossy that was not available for US purchase. If you want the name, let me know, I can figure out where I put it or comb my past Etsy purchases.