How do you prepare layer mash?

So, I've been feeding my hens Otter coop organic layer mash. I've been cooking it like porridge for 10 minutes in a pot on my stove. I've also been putting the pot and the feed bowls through my dishwasher. This was a Mistake. The mineral supplement grit in the mash has lodged itself in the inner workings of my dishwasher and ends up baked onto my dishes like concrete. Tried Finish dishwasher cleaner. Tried Draino. Next I'm calling the appliance repair guy. If I feed them the mash dry they waste all the powdery stuff that's supposed to be nutritionally important. Just wondering if it's even necessary to cook the stuff or can you just dump hot water onto it in the feeding container? Then clean it with a hose. At the bottom of the garden.