Since you say you use a sharpie, it might not hurt to try with a pencil. In most drawing classes, you'll learn with a pencil first. It's generally easier to control than a pen and you might find it easier to shade. I've basically been learning by studying up on anatomy and just drawing from photos. Learning anatomy is important, otherwise you end up with creepy looking drawings which are shaded realistically, but the features are in the wrong place (I used to do those. )You don't have to smudge with a smudge stick or a tissue. I don't smudge mine, I just like to shade with the pencil. I prefer the look, but experiment and see what works for you.
If you're having trouble with shading in general, it's probably worth doing some things like this to build up your skills: [link][link]