When I rode Brooks Pros yyears ago I experimented with using more Proofide v. less. Multiple coats did not do much good compared to the improvment in surface texture I got with one coat.

I also found that Proofide is not a waterproofer. It did not keep my saddle from absorbing water.

What did it really do? Well I guess I don't really know. But I would rather use something innocuous than something that could make the leather collapse.

I did think the leather felt better after I used it.