Richard is totally right. When you want to run-in a brushed electric motor, the first and very important thing to do is to adapt the brushes to the collector. Achieving a good aadptation is better made with low currents, for 380 motors the thumb rule is running it with a single AA cell (at these low currents you don't need high discharge ratings) of between 1200-2500 mAh in one direction and another full cell in reverse. in aeromodelling we attach a cheap prop direct to the motor shaft in order to adequately ventilate avoiding the slightest increase in motor temp and mounting the motor to a simple motor mount, sometimes even a vise. Wiring can be made with crocodile clips, again, low amperages permits.
Hope it helps