Will he sleep in a sling? That's one way to help him and see to your DD at the same time. Or the pram?
I know lots of people - that nurse included - will disagree with me, but I don't think you can teach a baby to sleep alone. You can help them along if they're ready for it, but if not you're left with either finding a way to get by in the mean time or forcing them.

What help do you have to call on? Can you get day care or babysitter to help with DD? A cleaner to keep the pressure off you at home? Do you get sleep on the weekends at least?
I really do wish I could guarantee you some sleep some how