Anything with ammonia will hel relieve the stinging sensation where the stinger(s) entered the skin. Keep the ammonia away from his eyes! As other FReepers have stated, urine also has ammonia and can be used as a field expedient. If the stings don’t appear to be too painful for him, just some baking soda and water paste should bring relief.
I sprayed windex around his neck, and legs....I checked his gums, they seem to come back to pink pretty quick.