Is there a reference or some sort of guide to help identify fake imperfs and part perfs?
In this case it's easy. The vivid bright red color of the $1 issues only exists on late printings. Early printings have a less saturated, more subdued ink color. A good way to compare is to look at the $1 imperfs. That is the color the part perfs should have. While not all late printing have this bright red color, no early printings have it, so it is an immediate disqualifier.
There has been at least one example of (supposed) R69b that is a horizontal pair imperf vertically, *but* it is not a real R69b. The color is that of late printings and the consensus is that it is an EFO misperf rather than an intentional part perf. It was in Eric's inventory for a while (he was trying to sell it as a part perf pair), but when it went to the PF it did not get a cert as a part perf. I spoke with both Richard Friedberg and Brian Bleckwenn about it at the time. Everyone agreed that it was not a true part perf.
One thing you also have to be wary of are imperfs that have been perforated to create part perfs. Those are especially insidious, as they can be quite convincing compared to trimmed perforated stamps.
Here are three examples of bogus part perfs that I have in my collection as reference items. In each case, the nature of the perfs is the giveaway (although the color on the last stamp is a negative indicator as well as the late cancel date):