Ease the loco close to where it needs to be for loading, stop it and then set the brakes to lap with about 15-20 psi then crack the throttle 1 or 2 notches then back to zero. This technique will move a consist 1 car length at a time so you can load. After a car loads the brakes will be set so you have to adjust them back to 15-20 psi then repeat.
Bob