This animation was created in Adobe Animate and took about an hour and a half to two hours to create. There are some places where it should be cleaned up, but this is just an example so I wasn't striving for perfection.
I drew each stroke on its own layer, and then created a mask that gradually unveiled the new character. I used shape tweens on the mask to get the computer to fill in the frames between "key poses" in the mask's unveiling. I realized towards the end of creating this that shape hints would help make this animation smoother, particularly for strokes that change direction (that's why you see some wiggles in the animation).
You can also create each stroke on its layer, over a few key frames erase a little bit at a time, then reverse the frames and fill in with shape tweens (using shape hints).