Hi!
Putting seeds in paper towel after ~24h into a cup of water is also my favorite technic. But, for some times, I've used old unknown seeds someone give me, and this technic didn't work all the time. The problem is that the seed shell getting harder with time.
So I start to use Hydrogen Peroxide solution (some drops of a 3% food grade one, into the cup of water) because it's help to soften the shell. Bubbles will appear around the seeds because the molecular instability of the HโOโ made it release Oโ.
I reuse this solution when seeds goes into paper towel. Again, the release of molecular Oโ will help the first root to spread, because you'll be sure they'll receive enough humidity and oxygen at the same time.
I recently tried this technic with breeder seeds and I was amazed to see how fast the shells open and roots grow strong into the towel paper.