I use coffee grounds on my blueberry bed but I also use a Soil Acidifier and bone meal fertilizer.
I can't remember the name of the acidification but it's in the picture attached. I haven't had much luck with the PH analyses like the one that you stick in the soil like Pirl above, but his looks more sophisticated than the ones that I've tried. I bought a soil test kit two years ago, but that's difficult to use too.
