I use a fair amount of edge highlighting with my models. It looks as though you’re using the flat of the brush to apply a line. That’s very, very difficult to do neatly, leading to a wobbly, somewhat messy line that you have. Try getting some paint on your brush (ensure it’s thinned so that it has a nice, smooth consistency) and then removed most on your palette. Then, using only the edge of the brush, drag it gently alonly the sharp edge of the canopy that you want to highlight. The paint should only go on to the sharp edge, creating a clear and sharp highlight.
For highlighting Khorne red, I would use wazdakka red followed by evil suns scarlet closer to the far edges of the canopy, where they meet at a point. If you wanted to highlight further, move into a more cream range, as orange highlights on red often look a touch unnatural.
Hope this helps somewhat. Drop by the projects board and take a look at the work of some of the guys there as some do it pretty well.