Suggest obtaining road maps from the counties.

I remembering watching loading from one public road overcrossing. Bring binoculars and telephotos.

There are many county roads; some paved. I remember seeing no gradecrossings - all overcrossings. Turnoffs into mines, and off-limits lines, are well marked.

There is one overcrossing of the mainline, near a mine turnoff, with always at least one train visible and moving.

Add Donkey Creek; more perpetual motion. Likewise Crawford Hill.

You will receive lots of suggestions, plus corrections to my offerings.

The only store between Gillette and Douglas is at Bill, and possibly Wright, so be prepared.

You have David's Timetable.

The BNSF / UP spurs are listed. These lines stop at the connections to the mine trackage. Contractors operate the trains thru the loadouts.

Your request was for "the best view of a loadout". Such is always in the eye of the beholder.

Study the trains for automatic-air bottom dump, manual bottom dump, and rotary dump.
"Somewhere out there" is a train with electrically controlled air brakes.
The automatic-air cars will have polished bumpers on the corners and air lines between the cars, about two feet above the couplers. The electronically controlled air brake cars will have electrical cables a few feet above the couplers.

Far more than you wanted. Visits to PRB "ain't cheep". I urge that you learn as much as you can;