Switching between first and third

I've never really written from first person POV before; I almost always use third, except for a couple vignettes. But I've really come to enjoy writing from first person. Much more space for character exploration -- of the MC at least -- and it's interesting to have the reader only see every other character, every situation through one person's eyes. A lot of opportunity to skew something and (maybe) catch the reader off-guard a little later. Keep them interested, keep them wondering.

But I'm working on two stories right now. One is first person and the other is third. And damn is it hard to switch between the two. I thought that keeping track of which character I was writing from was hard enough but trying to remember that, no, I'm not actually inside Jace Taggert's mind is even harder.