i can. I've nevere actually rendered before. But the way you are doing it is horrible. Learn to use the pen tool. I have a pen tool basics tut in the Basic tutorials section i reccomend hitting up if you want to render. It will still take some time but it will be much better than painting.

Ergh if pen tool is out of the question the polygon lasso tool would work well as well, but..you not going to be able to get rounded corners so i would highly reccomend not using it.

which ever tool you use you trace around the figure, then you make sure it gets selected (for polygon tool is automatic, pen tool CTRL click the path). Then invert it and delete the outside of the stock. Basically like cookie cutting, except your making the cookie cutter by hand.