The Scrubba is the Sailormoon combined with a Touchdown Raiz. Or a tapping Gumbi.
Once you know how to do the two prerequisites, TD-Raiz and Sailormoon, this trick becomes very easy.
01Sailormoon
The first progression is a sailormoon. It should be one where you flip over a little bit rather than going from side to side. That will make the transition to the Touchdown Raiz easier.
02TD-Raiz
The hardest part of learning the Scrubba is learning the TD-Raiz. It can be a very confusing trick at first. Make sure you have a comfortable Raiz before you learn this.
03Scrubba
After that just put the two together. It really is that simple. Make sure you spot the floor the ENTIRE time. It will prevent you from going side to side and makes it swingable.
Tips
Do not face the ground for too long for the first touchdown. It should be very brief and fast. It's just a tap rather than a real handplant.
Keep your chest up and open the entire time. Do not hunch in as you perform this trick. All the same technique that applies to the TD-Raiz, also applies to this trick.