My darling Cavalier, Pretzel, gets yucky tear stains that don't smell too great. Well and Good Tear Stain for dogs cleans them up.
Pretzel, like many of the Cavalier King Charles Spaniels, I've lived with likes to sleep on my head. Luckily, I'm bald and this serves as a heated, and kinda snuggly, stocking cap. Unfortunately it can smell really, really bad when her tear ducts have formed crunchy masses of fur under her eyes, and around her snout.
The stuff works quick and easy, just apply the remover to a cotton ball or a paper towel, and wipe away the stinky stuff.