There are several ways to improve the grind consistency using a blade grinder. Firstly, pulsing and shaking while grinding will offer better results than settling for one long grind. Secondly, you can use a sieve to remove the larger chunks after grinding. Finally, try spreading the grounds over a paper towel, then pour the coffee into a grounds container. The coffee dust sticks to the paper towel, allowing you to discard these very fine particles. Doing this should leave relatively uniform grounds for brewing.