Welcome to OFF.
First: it is ILLEGAL to "target" Bull Trout, in most of our streams. I suggest viewing / downloading regulations, from the Oregon Department of Fish & Wildlife (ODFW)--so you don't wind up with, a HEFTY FINE, have your gear confiscated, etc.
The John Day, during the time that you will be here, will largely be a Small Mouth Bass fishery. But I believe it has, a Redband population (but will leave this to others, to verify). It also appears that, all JD tributary's are CLOSED. You can view the reg's, on page 67 of the 2015 reg book. Then double-check, when the 2016 reg book is published (which should be very soon).
The JD, does have a population of West Slope cutts. But angling for them, may not be good in the heat of an Eastern Oregon summer & low water flows. Here is some additional info:
Good luck.