Tip to make soft idlis: soak a handful of thin poha for 10 mins & add to the rice-dhal & grind it... don't add too much, else the idlis will be way too soft to handle...
I used to make idli batter with 3:1 ratio if using mixie & 5:1 if using grinder... Soak rice for 4-5 hrs & dhal for 45 mins...