Hm. My best tool for this is a small slot bit for a drill, and a short drill fixture meant to hold those little bits. But the shaft is very small. Difficult to turn.
And actually, perhaps the biggest problem is that the lower air box is in the way. This is one of those rare times when I wish I had smaller hands. Here is a question I unfortunately probably know the answer to:
Can I make this adjustment with the lower air box removed? If I say "pretty please," then can I?