I have tried a lot of fertilizers for Blueberry's but this is definitely one of the best. I like to use it by mixing it right into the soil. (it can be applied by top dressing too) Best time to apply would be early spring.
Look how good mine look! Also after they are planted its good to use pine bark chips to cover them. Much better than mulch or stone. I found out using multiple varieties often help pollinate bushes better producing more berries.