It is hard to do if you don't start it from the beginning.
The breeder I'm buying a doeling from does it this way as well. Which is the way I would prefer to do it.I did this last year. I left them with their dams until 2 weeks old. At 2 weeks, I started separating at night and offering a bottle in the morning. If they took the bottle they could go back with their dam afterwards. If they didn't, I kept them separated until they did, offering the bottle a few times a day. But separate at night again even for the ones who did take a bottle. Most of them caught on very quickly and it made a huge difference in the friendliness of my kids, and milk test days weren't an ordeal.