I've never heard to using grain. Hmmm. But then you don't you need to remove the sprouted stuff you don't want?
I've used commercial rooting hormone found in any garden section of stores. I was told it does need to be fresh. So check for a production or expiration date when you buy it. And then if you need to use it later I was told to use it within a year.
I too have found that most things will just root on their own in soil. I never saw a big impact with rooting hormone. But then again I was rooting cuttings of things notoriously easy like coleus, chrysanthemums.