Direct Publisher uses a feed file to drive the channel. You'll need to create and manage either an MRSS or JSON feed file that describes your channel content. Having said that, you should be aware that Direct Publisher does not currently support a subscription model.
I've never done that. But, if I was switching from SDK to Direct Publisher, I would create it as a separate test channel first. Then, when the "kinks" are all worked out, I'd publish it and remove the old SDK channel.