I agree with both of the above posts. There really aren't any trailheads that you can't access with a horse trailer. Sure, there may be a spur road that goes a mile or two that I wouldn't take a trailer down, but the horse guys don't hesitate to ride their horses that last mile.
There really aren't many (if any) "get away from everybody" places in the Greys. While there are a few good bucks, it is over hyped for the most part, and very few first timers in the greys score on huge bucks. In fact, most people that hunt it regularly don't kill huge bucks. They just aren't behind every tree.
There are decent numbers of solid, nice bucks, and most people shoot the first one they see. It can be a fun hunt if you don't have unrealistic expectations.
In my experience, thinking you can "out work" or "out hike" everyone else in the greys is an unrealistic expectation.
Learn a particular drainage well, the deer's patterns, etc, and you will increase your odds more that just looking for some mythical unknown big buck hideout.
Bill