Ricky, before you cover that primer with your chalkboard paint, try a small test swatch. It might not be strong enough to work well through a layer of anything else.
I'm really sorry to hear about your bites. I expect you've tried ice by now. It's probably well past the point where baking soda would do any good. But there's a product out there called "after-bite" that seems to really help with various kinds of stings and bites. I think it's actually made of (oddly enough) meat tenderizer. I've had good results, even if I don't get to apply it right away. Worth a shot, perhaps.