I don't wait for rain, but when I see there's going to be a few days of rain, I try to get some seeds out there before it rains. A few days of rain might give the seeds a good start, and then, you could mulch the seedlings to help them make it to the next rainfall. You could use a handheld tool to cut competing plants like grass and use them as mulch. If you can spend a little time every day or week, then you'll figure out what works.