How large is the kennel that you potentially are keeping a cat in for weeks?
The kennel is 2 ft wide, 4 ft long, and 3 feet tall.. It's big enough for me to sit in there. There's a litter box and hammock.
I only use this method for those hard to handle or very shy kittens. Adults have the run of the room with the kennel has a hiding spot. The longest a savannah was in the kennel was 3 days, Kirby. The feral kittens in the neighborhood were 2-6 weeks, then they went to a local rescue. The longest was the bobcat kitten, 9 weeks (the only bobcat in which the handler can groom at the wildlife rescue).
They have to trust you first before they are comfortable to play with you. A cat will always chase anything small and moving fast. As soon as they see another animal bigger than them (human), they will flee, especially kittens. When they associate you with food and a neck massage, they will come to trust you. Afterwards, they start to form the bond.
A well socialized kitten from a breeder will not require drastic measures, but not all breeders are the same. My friend's F4 was from a well known breeder, but I can tell he was never socialized as a kitten. He acted more like a feral kitten. He did everything the breeder suggested; but his savannah (2yrs old now), avoids the family, skittish, eats at night, misses the litter box... and unfortunately he is thinking about it.. so you might hear from him Brigitte.
My rule of thumb is to make the extra effort to visit your breeder once before the kittens are ready, and watch how their cats behave with you around. Well socialized cats will be skittish at first, but will come out to investigate (F1 will greet you). If they have another batch of older kittens around, see how those kitten act around you. Because most likely, that's how your kitten will act when your kitten is at home. I've forfeited 1 deposit before adopting Kirby because the first breeder had 10+ adult cats and 3 litters of kittens. She said the kittens were all socialized... sorry, but one person trying to socialize 3 litters, maintain the herd of adults, and a full-time job... just isn't possible. And she ships cats...