rub him around in something weird
Your female dog may be in season if she does so, she also may be trying to release scent (maybe territory marking, maybe scent that she is in season) so that other male dogs know she's in her cycle.
The average dog has more than 200 million scent receptors
Burn an incense stick.
A female dog will never lose her distinct scent. The particular scent of her being in heat, however, ended immediately with the surgery.
The police dog tracks a criminal by scent.
you give the dog the scent and they can know the scent of the animal the master is ordering him to find
Keep in mind that what you think is stinky, is very different to your dog. Usually, a dog who rolls in some other scent is trying to either wipe out that scent by putting his own on it, or is trying to pick up that scent for reasons only known to dogs.
Female dogs give out a scent when they are in heed. Heed is when a female is in a position were that is the only time they can mate. So they have a scent that the Male dogs can smell that scent. Also it is in their Urine.
Yes, dogs have such a good sense of smell, they can even tell what gender, what age, what breed, if it is healthy, and if it is happy.
you evaluate them by how well they sniff
air freshener
Bloodhound