Can't comment on loadouts, but I have spent time at bottom dump power plants on NS and CSX. From my (albeit limited) exposure, trains were run through the dumpers by a crew called for that purpose, as opposed to a road crew. Once positioned outside the dumper, the conductor hunkers down in the dump house and serves as a communications relay between the dump operator and the engineer. When the dump operator sees that the car has not cleared itself or that a gate hasn't closed, the operator will say "stop" and the conductor will radio the instructions to the engineer. The dump operator resolves the issue, and the process restarts. The train will typically go through a dumper at ~2 mph. Between staging, stops and troubleshooting, the process probably takes 4-6 hours. I'd imagine rotary dumping takes more time. Individual results may vary
By the way, to see the first few cars dump is a pretty cool. Once you've gotten to the the 15th car, the thrill is over! Here's a good video link that shows the process (Australian, but same concept).