Vinegar and a dry brush are all you need.

Yes. Salt stains and mud are different problems, but the fix is simple.

For mud: let it dry completely. Then brush it off with a stiff brush. If you scrub wet mud, you push it deeper into the fabric or leather. Dry first, brush second.

For salt stains: mix one part white vinegar with two parts water. Dampen a cloth, wipe the salt residue, then let the shoe air dry. Vinegar neutralizes the salt. Works on most boots, leather, canvas, synthetics. Avoid on unsealed suede unless you’re prepared to brush it back up after.

One cheap brush and a bottle of vinegar. You’re done.