I ran a first test batch distilling spearmint.
I packed the top of the lid with mint, and ran it for about a half hour on medium. I ended up tying the lid down on the home-made distiller, to prevent steam leaks. I packed this fairly tight, so it actually backed up a little pressure pushing the steam through the mint (less pressure to push through the sides).
I just collected the distillate in a normal glass.
Really though, what would be ideal, would be a bottle with a very long, narrow neck, that could allow excess water to be drained off from the bottom. That way, the oil would separate cleanly, and not bead up. If it beads up, it's going to be hard to pull it off the top with a dropper.
The spearmint oil floating on top of the distillate. It's beading up. This would be enough to flavor several hundred toothpicks. Just dip the toothpicks in cup, and it will pick up the oil. It's extremely strong.
Also, I used a medicine dropper to pull up the oil, and ended up with 2 ml from one small bunch of spearmint. I suppose if I distilled all the mint, I'd end up with a small bottle. A little goes a long way though.
You'll need a little air in there to push the oil out (floating on top). You can discard the water (at bottom).