Ok step one: Decide the main positions Make sure to decide what you're going to animate. For example, in this animation, it goes ready fight position, kicks, punch. Those are the 3 main positions! I drew the 3 main positions BEFORE I did what's in between to make it smooth.

So, first off: Read-pose, Kicking pose, Punching pose. Try to practice that, first. Make those 3 poses.

Then, you do what's in between to make it smooth! I suggest hitting 'copy and paste' and adding a layer in between, copying the 2nd form, and putting it on the first, erasing it lightly, so you can see the first and second form to determine what position goes in between.

And that's it! Super simple