I'm wondering if coverage improves with better sticks.
The quality of the sticks will help them glide easier across the paper, for sure. They're all made with various combinations of just pigment, oil, and wax. Cheaper brands have more wax and are crumbly and stubborn to blend.
But here, for your sketch above, it's more technique. You might want to try covering larger amounts of the paper - for sky, or general background - by laying the stick on its side and sweeping it across. I like my Cray-Pas for this: I break off an inch-long piece or so, and then remove all the paper. I can cover even a 12x16 sheet pretty fast. You can layer over it several times in this manner if you like.
It's all personal preference. For a sketch-like look, you can use them like you did above, just with the ends, to get a fast and nice look. For sharper lines, take the ends and rub back and forth on blank scratch paper to make a nice, sharp round edge. (I waffle between that technique or just grabbing colored pencils, depending on what I'm painting.)
Looking quickly through my WIP pics, here's one where I used the side of an OP to cover the background, after making a sketch with graphite and colored pencil. You can see the marks are a good inch wide. Because OP's are a dry medium, you can get in closely. I ultimately filled in the whole page around the portrait with these deep red. (For some reason I was suddenly obsessed with getting a deep red portrait background when I did this. Who knows why.)
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If you want to even it out for a nice, solid color, another trick is to get a cheap artist brush and dip it in a bit of Turpenoid. This is odorless, artist-blend turpentine, and it's a fantastic method to learn if you feel like exploring your options with OP's. More layout in cost, but a small bottle will last for a long, long time.
So the brush smooths out all those lines and you get the even color like this:
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You can see the brush marks, top and bottom. Takes 5 minutes to do and, depending on your paper type, maybe 15-30 minutes to dry completely. And you can pick up your OP stick and go right over it. It's really cool.
Anyway - OP's can be fun, people say they're great for plein air (I'm not into that) because there's so little to carry, including no water. Just something to ponder.