Well, you're not actually "growing" them in the paper towels, just using the towels to pre-sprout them. This works best with seeds you can actually see (
). I use it mostly for starting morning glories because I never have any luck stuffing them in pots. But it's also useful for older seeds that you're not sure are going to germinate. Basically, you just spread the seeds onto a fairly damp paper towel, fold it up, stuff it in a plastic baggie and set it some place warm (I tuck mine next to my monitor so I don't forget about them). Once they sprout, just separate them and put in pots. Some seeds will sprout overnight or in just a day or two with this method. And if the seeds require light to germinate, you can do the same thing by putting the seeds on top of a couple of layers of damp towel inside a clear plastic container with a snug fitting lid and set somewhere they get enough light. Those will need spritzing occasionally to keep from drying out. Pretty easy for starting just small quantities.