I recently purchased a Weatherby Mark V that has been Ceracoted in black on all metal surfaces. The finish is great, but what I notice compared to my other Mark V's is that there is more friction when working the bolt back and forth. It does slow down the cycling of the bolt compared to how fast I can work the other rifles.
Is there a preferred lubricant to smooth this out, or another method to make it smoother?
Just run some regular bore oil on the bolt for your range sessions. The more you work the bolt while there is oil on it, the smoother it will get. I always run a bit of lube on the bolt body after a fresh coat of cerakote. It will smooth up over time. Just remember to wipe it down before you take it to the field so it will not attract dirt.
With the remingtons and stillers I coat here it seems the best thing to do is keep them dry and clean. Even dry they will work in and as the coating wears clean the "dust" off the bolt and the reciever raceway. When it mixes with grease or oil it gets gummy and sticky.