How did you do this? Someone mentioned that it looks like you used a wood burning tool, I think so too, is that what you used?
This could definitely be cleaned up to look pretty nice. Variation in line thickness is always preferable to the eye than just a single line thickness. That is how I would start cleaning it up. I would sketch thicker line where your non-smooth curves are. Go from thick to thin using a smooth curve. Something like a flexible French curve (if you can find one) can help you sketch flowing lines if you have trouble doing that freehand. Once sketched on the stock (you could use a grease pencil vs something like a Sharpie.) The grease pencil lines can be easily rubbed off if you aren’t happy with the design.
Once happy with the sketch, I would start with a small gouge (chisel). Wood only wants to be cut in one direction. Experiment with some scrap wood to understand how it wants to be cut. Once you get the feel you can look at your design and pretty much tell which way you want to attack the particular cut.
Your chisel will be at a rather shallow angle to the surface of the wood, almost laying flat. Your strong hand will guide the chisel and your weak hand will be resting on your strong hand to keep it from going where you don’t want it to go. You will take very small cuts, don’t try to cut what you want to remove in one pass.
Anytime that you are trying to get a lot of control of any hand tool you must be, what I used to tell my metal smithing students, tight. No not via alcohol but you need to be based. Anchor your hands, sit down as well. I also used to tell them that. When you sit down that is one less thing that your brain has to think of. Of course depending on what you are doing and how you are holding the stock that might not be possible. I have done a lot of work on gun stocks and grips while standing but if you can sit that is preferable. Sounds silly but it is something that I have noticed over the years, especially with students.
You MUST have a very sharp gouge, if you don’t know how to sharpen a chisel, you must get that skill developed before you go to cutting wood. Even if the gouge you purchase is sharp, it won’t stay sharp. You will need a “slip stone” when sharpening a gouge.
I hope this helps in some small way. If Duke City is anywhere near Beaver County Pennsylvania, I would be happy to have you come to my shop and give you a hand.
Your stock is definitely salvageable!