I just have two bits to add, both regarding bees: When a bee stings, it leaves behind its stinger, which is loaded with pheremones. These act as a warning signal to other bees--essentially, it marks the victim (in this case, your dog) as a dangerous enemy. Other bees pick up the scent of the pheremone and "storm the castle." That's why your dog had multiple stings.
Even on a relatively hairless creature like a human, it is difficult to find a stinger, let alone multiple stingers. On a dog, this is impossible. Make sure you give pooch a very deep shampooh, followed by a thorough brushing.
One other thing about bees: They are at their most dangerous in the spring and fall. Something about cool nighttime temps makes them sluggish, both physically and instinctively. It is not uncommon to find all kinds of bees--honey, bumble, hornet, wasp, whatever--flying slowly and aimlessly or even just walking around on the ground during spring or fall. They are also more prone to overreact these times of year. Their instincts just kind of go haywire, and they react to just about anything as a threat. Your dog probably didn't do anything out of the ordinary, anything to provoke the attack--he was prolly just in the wrong place at the wrong time.
I gave him a long shower, and brushing yesterday, but without soap.
We will give him a shower with soap today.
Thanks!