Corn Gluten to combat crab grass??

Hello,
I'm a Brit living in Italy & have what appears to be "Crab Grass" in my lawn, which I'd like to remove. Not wanting to use herbicide, I've now read a lot of info about Corn Gluten, but have not been able to trace one supplier in the UK, let alone in Italy, despite finding lots of people referring to it.
Here in Italy, I am literally surrounded by maize growers, and it's easy enough to buy corn flour in the supermarket. Can I just use this or do I need to buy some special product??
I have a very small lawn and don't need much.

Many thanks in advance.
Kean