The reason dogs chase bicycles has mostly to do with instinct. To them a bicycle appears as prey, and as a result they give chase. This behavoir may even override scents, so spraying your bike with "big dog" scent, even if available, might not accomplish the desired result.
I rarely get dogs chasing me simply because there aren't that many unleashed dogs and/or strays where I live. The few times I do, I simply accelerate smartly and go as fast as I can for a few blocks. If the dog can even keep up (most can't manage the 25 to 35 mph I reach when I do this), it usually tires of the chase after a block or two and gives up. Dogs aren't prone to chasing "prey" once out of their "territory". Also, many breeds can deal only manage quick sprints, not extended high-speed running.
I don't know if you're a strong enough, experienced enough rider to do what I do, but I can say it's worked every time. In fact, I've found the majority of dogs start losing ground even at 20 mph. Don't forget that the dog is usually standing still when it first sees you and decides to give chase. By the time it accelerates up to speed, I find I'm often half a block away even just holding my normal 21 to 23 mph cruising speed. If I notice it gaining, I will start accelerating immediately before it has a chance to catch up since I can't go from 20 to 30 as fast as a big dog can. Short of being chased by a greyhound, which hasn't happened yet, this method works well for me.
Another thing you can do if you see that you can't outrun the dog is to quickly come to a complete stop and remain absolutely motionless until the dog loses interest and walks away. When it's a block or so away, just ride away very slowly so as not to attract it back.