By default, Krita has all the brushes you need to help you get started. And it won’t take you long to realize that this feels like drawing. Here is a very quick demonstration I did just now.
There are many ways to use a brush and I would say that every artist is different in how they go about using it. However, for me personally, I find the Basic-5 Size Opacity (with its default settings) brush extremely helpful to lay out the rough sketches. I draw lightly with this brush, and strokes might get bolder if I press harder, and I don’t have to worry about making any mistake because I know this is just brainstorming. The advantage with a brush like this is that it gives room for interpretation once I switched to the other brush for outlining. Strokes might fly here and there, thin here and thick there—it doesn’t matter. The whole idea behind this brush and phrase is to be free and not think too much. Here’s an example:
After the rough is done, I switched over to the Basic-5 Size brush, with the “Dynamic Brush Tool” instead of the regular brush. This is so I can get a much smoother line without trying too hard.