Hi Andrew,
Welcome to our forum!
If you are using line plots (e.g., Plot command) animating with a mask can be jittery as each point is ‘unmasked’ and the line jumps when you have space between points.
Using a reveal would be the way to go, as the line is drawn but just not shown until the animation variable moves along.
If you look in the on-line examples, the Simple animation example may be helpful.
Just in case you have not seen this, we did a webinar on animation last year where we used a line graph example:
https://youtu.be/HPko5QNH3f4
Here is where we talk about using a reveal:
https://youtu.be/HPko5QNH3f4?t=1248
Here is a screen shot of the example file … Does this help you?