Sketchy lineart in after effects

Trust me, drawing anything like that using After Effects Shape Layers is going to take at least four or five times longer in After Effects than it is in Illustrator and you will not have access to nearly as many time-saving tools. No professional motion graphics artists would try and recreate or edit anything like this directly in After Effects:

Every one of those black lines that have a brush look will have to be a filled shape in After Effects or a separate line on a separate layer with a distortion effect applied. In Illustrator all you have to do is assign a brush to the brush tool and draw.

If you just want to create the drawings After Effects is the wrong tool. It would be like trying to drive nails with a screwdriver. You might get it done eventually but it's going to make a mess.

If you want to animate those kinds of drawings you need to create the artwork in Illustrator as a layered document, import as a composition retaining layer size and then animate the composition that AE creates. 

It's as easy as this from the Illustrator User Guide and can quickly get really fancy with just a little practice like this: