I like to test the soil in the drain holes at the bottom. sometimes the pot feels light but I test the soil at the bottom and it's still damp. I let it go one more day and water. I haven't had a single problem with this method.
it certainly does respond well to cloning. I just got a clone from a buddy. It was bout 3/4" tall when I got it(2 days ago). It's doubled in size both days I've had it.
If it's possible, I'd save up for a better PPM meter. It will pay for itself 100 fold. I've never had luck with cheap ones. It could just be my luck though