How I finally saved a trashed old leather belt - steps that actually worked

Did pretty much the same routine on a belt I found in a box from my dad's garage, except I used saddle soap instead of the vinegar wipe. Worked fine on the grime but I think the vinegar approach would've been gentler on the mildew spots, so I might try that if anything else comes out of that garage smelling musty. One thing I'd add is to test the conditioner on the back side of the belt first, near the tip where nobody sees it. I used too much on my first go and the leather went dark in a blotchy patch that never evened out. Thin coats really is the whole secret, like you said. Also second the point about drying slowly. I once left a belt across the dashboard of my car on a summer afternoon and it came out warped like a banana. Took me weeks of conditioning to get it wearable again, and it never sat flat after that.

On the stitching, a curved needle helps if you're going through two layers at the edge, since a straight one fights you the whole way. Mine looked rough for the first inch or two and then my hands figured it out. Good enough that nobody notices unless I point it out.

Storage is the part people skip and it's why the mildew keeps coming back. After I fix up a belt I hang it on a hook in the closet with air on all sides instead of coiling it in a drawer. I do this for every belt that leaves my bench, somewhere north of 300 over the years, and the ones stored coiled in boxes are always the ones that come back spotted. If your closet runs damp, a cheap humidity gauge on the shelf tells you more than any product will. Anything sitting above 60 percent for weeks is asking for trouble.

First time posting here after lurking a while. I don't have a belt but I've got my grandpa's old wallet with the same white fuzzy stuff all over it, so this thread is timely for me. Question though, does the same routine hold up for something that folds a lot? A belt mostly lies flat but a wallet gets bent at the crease every time it's used, and I'm worried conditioning it will just soften the folds til they crack through. Or is that overthinking it and I shold just follow the same steps and see how it goes?

That vinegar wipe trick works on other stuff too, I found out by accident. Had a pair of my uncle's old work boots come out of his barn covered in the same white fuzz, and the diluted vinegar on a barely damp cloth cleared it up without stripping the finish like stronger cleaners did. The one thing that actually made the difference for me was an old toothbrush for getting into the stitching grooves and around the eyelets, soft enough that it didn't scratch but it pulled the grime out of the seams. Let them dry slow like you said and they're still in rotation two winters later.