Not a fine art. We used to put a kid or two or three in the back of the pickup and have them sling it out as we drove around the ring. You can see where you missed in just a little while and then go back over.
We have also used a tractor mounted seeder, but there was too much maintainance ie, scrubbing and oiling, to be fun outside in freezing weather.
The first method gave the kids something to do too.