So I tried it again, and Q does work but it doesn't work if I'm already attacking. I imagine this is why I struggled to activate Q the first time because it didn't feel very natural for me to stop attacking.
Ah, ok that makes sense. I considered Q as a separate attack, and after a basic attack the hammer resets and gets ready for the next attack. It didn't make sense to have Q work once it already hit the enemy with a basic attack. I see what you mean about it being unnatural, and I'll play around with the controller further to find a fix.