P.1 After Effects

This is one of my effects which the functio of thi is to have the bubbles appearing one by one as you can see in the images below.

 I out the first bubble first by putting the opacity to 0% then whenever i wanted the first bubble to appear i will move the opacity up for example to 60% as i didnt want it to go up to 100% as it looked a bit fake.

 Then after the first bubble appears, i changed the opacity of the second bubble. I did exactly the same process for the second bubble.
I changed the opacity for this one after the first bubble has appeared to give it the effect of a thought coming.

For the last one i did exactly the same process but changing the opacity later on when the clip is about to end.