The treatment aisle is confusing on purpose. It is much simpler than it looks: the material decides the product, and almost nothing else does.
Almost every waterproofing question turns out to be a material question. Wax on suede ruins it. A water-based spray on a heavy work boot in constant mud washes off in a fortnight. A silicone aerosol on a membrane-lined hiking boot can close the pores the membrane needs to breathe through. Nothing here is about brand loyalty; it is about matching a chemistry to a surface.
The second thing worth knowing is that most treatments have a moisture instruction, and most people ignore it. Nikwax tells you to apply Nubuck & Suede Proof to clean, wet footwear. Atsko tells you to preheat clean, dry boots before Sno-Seal, and not past 120 °F. Those are opposite instructions, and both are correct for their own product.
Nikwax
The maker's directions say apply it to wet boots, which removes the step everybody skips.
Skip it if: Your boots are smooth full-grain leather - this is formulated for nubuck and suede, and Fabric & Leather Proof is the sibling you want.
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Every manufacturer in this category says the same thing and it is the step people skip: proof a dirty boot and you seal the dirt in. Nikwax sells the cleaning gel and the proofer as a two-stage system for exactly this reason -green for clean, purple for proofing. Salt is the worst offender, because a dried salt crust sits between the treatment and the leather. If your boots have been near a gritted road, they need the salt off first.
There is no universal interval, and any site that gives you one is guessing. The honest test takes four seconds: flick water onto the toe. If it beads and rolls, the finish is intact. If it darkens the leather and sits there, the finish has gone and the boot is now absorbing water on every wear - which is the beginning of the whole chain again. More on reading that test.
A boot that has stopped repelling water is a boot that will be soaked by Thursday, and wet leather is what road salt attacks. Waterproofing is the maintenance end of the chain: it is what stops the other three problems starting.
Four proofing sprays ranked on published directions, material range and bottle size - including which ones you can apply to wet boots.
Top pick
Nikwax Nubuck & Suede Proof
Our best waterproofing sprays pick on this page.
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Waxes, oils and greases for smooth leather boots, ranked on published ingredients and application instructions.
Top pick
Atsko Sno-Seal Original Beeswax
Our best for smooth leather pick on this page.
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Three water-based proofers cleared by their makers for suede and nubuck, compared on directions and coverage.
Top pick
Nikwax Nubuck & Suede Proof
Our best for suede pick on this page.
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Water-based proofer against beeswax dressing: opposite application methods, opposite materials, and a clear rule for which you need.
What wax, spray and cream each actually do to a boot, and the single question that tells you which one you need.
The full waxing method for smooth leather boots, including the published 120 F heat ceiling and what wax does to color.
The published method for proofing suede and nubuck - brush first, water-based spray, 2-minute dwell, and no wax ever.
Why no maker publishes a reproofing interval, and the beading test that answers the question for your boots.
Why winter defeats ordinary waterproofing, and the October-to-March routine that keeps salt out of the leather.
Wet, stinking, salted and dried-out are not four separate problems. They are one chain, in that order, and fixing the first one properly is what stops the other three.