Unfortunately with that mix, PR will dominate and make up approximately 80% of the stand. It is pretty vital that you keep the initial PR mowed and the seedbed moist so that the CRF and KBG can establish. Over time the PR should die out in your area and the other two should eventually become the majority constituents. I would have gone with a mix 10% or less PR.

For reference:

https://turf.purdue.edu/tips/2009/08102009_grassmix.html

Edit: I failed to see you are overseeding. So all is not as grim as I make it sound. That said, unless your lawn is quite thin or you thinned it out with heavy core aeration or verticutting, most of your overseed will be PR only.

Thanks mishmosh. So I should continue to water frequently (3x per day, 15 min each) even after the PR establishes while waiting for the KBG to germinate? What about general use? Should I stay off it until the KBG germinates? Or am I ok once the PR comes up?

Also, this may be a dumb question, but what's the main issue with PR? I did see in the article you referenced that it's more prone to disease, but other than that, what are the drawbacks?

I wouldn't get crazy with the watering. The temps now don't demand it and it's easy to overdo it. That said, if you want the fine fescue and KBG to germinate, make sure the upper soil is moist. Basically what I am saying is, keep watering but survey the lawn to make sure it's not too wet

My bias against PR probably stems from my preference for KBG. My lawn doesn't need the traffic tolerance of PR. I've used elite varieties of PR and all seem to get hit with disease where my KBG is unaffected. I don't like the look or feel of PR compare to KBG. In some areas where it's 100%, it just doesn't look nearly as good as KBG. I've seen significant losses with a cold winter but snow cover can reduce that risk. I would have to admit that for overseeding, it is a great grass. You'll get good germination overseeding a healthy lawn with just "spread it and forget it" and watering.