You can get them most easily by getting to Elder 5* and doing the Remobra quest.
I don't believe there is any other way to get it until at least HR4, and you have to fight a Tigrex to get to that point anyway, so just practice on him.
I beat him first try with full Blango Armor, Eager Cleaver, 10 Mega Potions, 10 Potions, 10 Herbs, 10 Blue Mushrooms, 5 Flash Bombs, 10 Flashbugs, 10 Bomb Materials, and the first 3 Combo Books.
Just go at his side when he charges, unless you really want to break him up, which shouldn't be a priority until you are more proficient.
For anyone who doesn't know, I used to be Tree Afro.
You will come to understand fear as I have...
If you were me, you'd want to be you again...