Sanding. Sanding is one of those things that makes me think we should rename this forum from "405th" to "punishment gluttons that like to sand too much."
Lol if you want really, REALLY good results, unfortunately, you'll have to put some effort into sanding.
Another thing that I find makes or breaks a project is attending to the little details i.e. seams. Do great on your seams, make sure everything is aligned, and you're golden.
That rifle prop looks amazing so far, by the way. Keep up the good work!