Easy

Shoot herman (green shot) which will get you a multiball.

Medium

Play all the modes. Shoot any given shot 3-5 times to qualify the mode which takes you to a mini wizard mode which is fun.

Hard

Shoot it into the grandpa racecar. This will collect a bonus for super jackpots. The key here is to hold off collecting this for as long as possible because the jackpots stack super linearly. This collect can be >100M points if you have a bunch of jackpots.

General notes

Preferred is to do hard building super jackpots for balls 1-2, ball 3 collect the super jackpot to ensure the payoff.