What exactly is hard and soft feathering in chickens? Is it how compact the feathers are?That depends on your definition of difficult and easily.
Hard feathering is autosomal incomplete dominant. Your first cross will get one hard feather gene and one soft feather gene.
If you breed those F1s together you'll get about 25% soft feathered offspring.
If you breed your F1s back to a soft feather parent you'll get about 50% soft feathered offspring.
Whether it has two genes for hard feather, two for soft feather or one of each they shouldn't be hard to tell apart so that makes things easier then dealing with hidden recessive genes.
I wouldn't consider it to difficult to breed out just gonna take a fair amount of throw away chicks but that's how projects usually go.