If you have an LFS close by, you can pick up some Aiptasia-X. It comes with the solution (basically concentrated kalkwasser solution), an application syringe with two tips and directions- everything you need to get rid of a hydroid.
I would just scrape it off or suck it out via siphon while doing a water change. I personally don't like the anti-aptasia stuff out... it causes them to super retract and then you're not sure if they're actually dead.
That's a good way as well. Sometimes simpler is better. I'm not sure how hyrdoids multiply, but if it's like aiptasia, make sure that you keep the siphon next to it when you scrape it off in case it releases any spores.