That seems to work but I think that if you could do it with the car stationary and the bleeders open you could get the air into the lines easier. The way I read the workings of the ABS pump the ABS motor builds up the pressure after the solenoids have released the pressure. Maybe we need to open each solenoid in turn and get the motor running thus expelling air from the motor into an open line.
The grass method may work but some air may just go back to where it came from.