They don't really need any different treatment. They're still chickens.
They tend to want to sit by the feeder more than foraging.
Some use a higher protein feed (20-24%) for the first few weeks. But then, some restrict feed to a few servings a day to slow growth.
The best way to do that is to keep them in the dark for at least 8 hours after the first few days.
I just let them eat. Sitting by the feeder and eating does tend to make it necessary to change bedding more often.
Cornish X can be processed at 3.5 to 4 weeks as Cornish game hens. Otherwise, you can start processing at 6+ weeks.