There's no easier way. Outside of super busy times like spring break and Christmas, it sometimes works to try a date range beginning on Sunday and ending Friday. Weekends are nearly always sold out these days. To book full weeks you forget have to book a year out or snag a cancellation.
I'd also recommend using a travel agent that specializes in Disney. Even better if you use one that specializes in Fort Wilderness reservations as they know the tricks of the trade. I use one and it doesn't cost you anything. You can probably Google to find one if you want to try that route.