2D Visual Effects

How do I actually do 2d visual effects in my game?

For example, I have a monster which can spit out a ball of mutated stomach acid which upon hitting the ground spreads out into a large pool, and It causes some damage. Just like Spitter in Left 4 Dead 2. How do I do this? Should I use After Effects? Or write my own shader?

Learn to use the built in animator, it’s quite useful.