I used TinyTask Portable on the first stunt mission, because it pauses the game during jumps for tutorial sake, allowing any lag to catch up, and I just recorded a run. I let this run loop for one day and got over 2,000,000, which helps in the later stages with expensive upgrades and cars.
Make the run on the very 1st stunt mission, each time the game pauses to tell you to move your fingers (mouse) up or to the side to do a stunt, allow about 3 or 4 seconds, to allow any lag from the constant re-loading of the stage to catch up. After you finish the run, make sure you record the key presses to retry the stunt over and over again. Then loop this and let it run for however long you want. As of this day I am on stage 4 so I don't have this achievement yet.