The process is really fun once you get the hang of it and it'll teach how a lot about how knit fibers interact with each other. Throw on some music and try your hardest not to go cross eyed or blind.
I just used a plain Hane's beater (my brother's), which is a ribbed knit. I'm not sure if I was just not unraveling all that I could, but I ended up with a bunch of vertical lines. And I like it that way.
So. The way to start this mess off. First cut off the bottom hem so you can start pulling down fibers at the bottom. You can use a seam ripper to start off grabbing loops, I just used a pin. Explaining what you want to pull is actually difficult. Just play around. Start pulling fibers down with the pin until the vertical loops start coming apart. Can you see that? No? Sorry, I tried...
Once you get about a centimeter unraveled, you can ditch the pin and start pulling with your fingers. Try pulling from the top and bottom at the same time, it's quicker and you get a lot more done at once.
You'll probably rip a few holes along the way. No big deal, who wants perfect meshy panels anyway?
Do whatever you want with this. You could made the back (and front, if you want) entirely sheer. Once I started, I really liked making these stripey kind of patterns. Here's what I ended up with. Looks like I was mauled by a bear, yeah? Perfect.