Is it possible to use 2 relays instead of a DC motor controller?
Absolutely, provided you don't need coasting. Connect the common terminals of 2 SPDT relays to each motor connection, and each of the throws to V+ and V-, connecting each to the same throw on each relay. Activating either single coil will cause the motor to turn in each direction, and activating neither or both coils will cause it to brake.