Some techniques I’ve used to create handdrawn looks:
Using Roughen Edges is a great way to create thick and thin line variation – and using a turbulent displace with small size can create a good roughened texture.
A large turbulent displace can make a straight line a little curvy, but use subtley. If you make the line a little wavy like that, CC Composite another copy of the original line below to make it look like two sketchy lines, then add your textured tiny turbulent displace over the top of both.
All of these effects can be randomised to create a boil effect. Select all your layers, use the search bar for ‘Seed’, and this is the expression I use inside their Random Seed value:
posterizeTime(5)
random(1000)
This can create some real genuine random handdrawn looks, although can take a while to render.