Yeah, usually the best way to fight these guys is through good old-fashioned technology. I mean, I've tried what little magic I know, but that always backfires. Last time I tried that, I was twelve, and I got grounded for raising the dead again, AND to top it off, it didn't work.
Okay, so what you need to know is that most aliens are susceptible to two things - electromagnetic pulses for their weapons and ships, and germs for themselves. These guys are pretty reliant on their technology, so the best strike at them is to hit them with EM pulses. The down side to this is that anything that can be affected by EM will be affected by the strike. That means cell phones, computers, most cars... But if you can lure them out to a place where the blast radius won't affect your own stuff, you can hit them where it hurts and get a huge number of them down in one go.
I happen to have a few EMP mines set up, I just need to lure them into the minefield. That's tonight's huge thing.