Quoted from Av8:
There are 5 main shots as on AFM (See Pic. Look familiar?). Each with 4 inserts and a Red "Shoot here" arrow. Shooting a shot 4-5 times starts/qualifies the Hurry up for that shot. Do this 5 times (each shot) for Total Annihalation MB. MM has similar Hurry up Jackpots also.
Let me know if Im wrong here.
Only 3 shots are required to each of the 4 main shots to start the hurry up. The key (if going for the 1 Bil hurry up) is obviously to get each shot to where only one more is required to start the hurry up & if possible start with the cow Ramp as that is the toughest of the 4.