Yeah, I'm pretty sure it is. I've only done it once, but I'm pretty sure I stopped spraying once I saw them. Once its male, its male. I imagine its the same as a regular bud, it just needs a bit of time to ripen.
I remember even after I pulled the plant and it was shrivelled up and dying unopened balls were opening up and pollen kept pouring out.
Saying all this, I've you've got some collloidal left, it won't hurt to keep spraying for a few days. The plant keeps growing and producing halls for quite a long time, its not a one off thing.
Just cut them down, grind the male flowers up and pollinate the females. Job done.