I think the way to "hide" the posts like you're speaking of is to back date all of the custom posts to a certain date in the past, and then put the link to the actual date on your journal.
For example, set the date to December 31, 1999, and tick the back date box:
And for your second part, maybe they find fonts that look like handwriting and skew the image a bit in photoshop, or they write the entries themselves and scan it it?