“Is bone grafting for dental implants painful?”

No, it is not painful.

I don't know. If teeth are being taken out at for an implant to be placed, the bone graft is done at the same time as the extraction, so there's no additional discomfort. If the tooth (teeth) are already out and now the bone graft is being done, I assume it's as uncomfortable as an extraction. But, again, I don't know. I've never had one done. Ask your dentist.