Well mostly with a sketchy style you do more basic drawing EG: rough line arting or a less detailed drawing because thats just what fits it.
There isn't a whole lot of dark/deep shading with a style like that. But if you were to do it you would do a pure black and just dip it all and in the edges you would have a scratchy look to it.
Here's some shitty examples that will get the point across. on the general idea of what to do. (none are mine)
https://orig08.deviantart.net/0412/f/...an-d9zxxf8.png
https://36.media.tumblr.com/8ccd69ac...2nn4o1_500.png
https://media.tumblr.com/tumblr_lsgc****SM1qcf0mo.png
https://comps.canstockphoto.com/can-s...sp19425041.jpg
https://www.designveryeasy.com/images...tor-140351.jpg
https://st.depositphotos.com/1168906/...nd-drawing.jpg