Oh, I know it's possible. I was just pointing out the logistics on your reasons. I have no issues with you wanting to lactate. Anyone can (yes men too), without having a baby. Yes, pumping can help. I'd find a guide and follow that if you are going to do it.
Just keep in mind if you are wanting to do it for the lactose intolerance... it won't help. It will actually probably make his issues worse. So tell him to take a lactose pill or something first. You can buy them at any pharmacy, probably cheaper at wal-mart.