Put your left finger on F6 and prepare to make a key frame.
Draw the first stroke at the beginning of the shading layer, then press F6, a key frame will be set automatically, draw another stroke, and then press F6 ... to repeat the work.
accomplish
The above two pictures are not animated for you, but we all write in this way. If there are a lot of words, it is enough to set about six frames for each word, otherwise the animation will be too slow. If it's just a word, you can make it into two layers with 50% transparency to create a little ink-breaking effect.