I have tried couple of ways, but please share your best practice for feeding a bitch in whelp. How much do you increase her food and when? Do you feed Performance, Puppy? Thanks in advance.

I don't feed puppy food until after she whelps. I feed her to maintain her condition. There is no percentage. If she's looking or feeling leaner (rib and spine and hip area) I increase her food. Some of my bitches have eaten almost the same at the end of pregnancy as at the beginning - they are so efficient. Others have needed a big increase in food. Always treat your bitch as an individual.