First off to me this is a classic case of posting more than one photo of a pen. I just never understood why so many people post 4 or 5 or more photos of the same pen turned upside down, inside out, backward, forward and all they show is the other side of the grain. If that is the best side show it. In this case you have a few different things going on and it would be nice to see better photos. A pet peeve of mine. Add that to the list of petpeeves
As to answer your question about sanding dust. Don't sand. Plain and simple. You figured it out on your own when you went from skew to finish. If you are proficient with a skew there is no better finish than a skew cut. If you look at some of my segmented pens I never used a piece of sandpaper. I went right from skew to finish. Works well.
From the photo you do need to work on your fit to the kit. Now this is all a learning experience but you are on the right track when it comes to making an intersting blank. Keep at it and look forward to seeing more. Thanks for showing and if you could post more photos it would help.
Upon further looks of your pen it looks like you tried to follow the contour of the curve with your dots . This would make for a nice look but it gets tricky on the amount and distance to keep symetrical. I still like your attempt.