But until you get your five posts, there's no reason why you shouldn't get a response here
Blueberry tobacco you say? Sounds interesting. First, you will need to find a tobacco base you like. This can be daunting, and depends on the brand of cigarettes or cigars, or pipe you liked.
Flavorings from different vendors work at different percentages. For example, my mother smoked marlboro reds for... a long time. She likes M-type tobacco that I purchase from myfreedomsmokes. It works best, in her case at 6% strength. Now, if I wanted to add a blueberry note to it, that was just enough, but still made the tobacco flavor shine, I would need to play a little. The blueberry flavor I have is blueberry extra from The Flavor Apprentice. It's noticeable at 1% strength, and full-flavored at 4%. Note that the "extra" means it's super concentrated, so less is needed.
Now that we have those numbers, my tobacco will need to be 6% strength, and just as a trial, I would start the blueberry at 2%. Then, I would play with the percentages a bit until I thought it tasted right.
That's just a simple 2-flavor juice, and you can add other things, like Ethyl Maltol to sweeten it up a bit and make the blueberry flavor stand out a bit, or Acetyl Pyrazine to round out the tobacco flavor, for example.
I know I ranted a bit, but was trying to be thorough. I hope I was able to clear it up a bit for you. Also, head on over to the DIY forums and read a bit, you may not be able to post yet, but you can sure read, and there's lots of info over there.
Good luck!