I have done a half dozen stocks from bare wood using Tru Oil and never used any sealer or filler. Key ingredient was/is patience. Make sure each coat is dry (it doesn't take very long) and rub it out. I use 4 ought steel wool. Then reapply, let dry, and rub out. Eight to twelve coats gives you a really fine fihish and you can rub it out to any sheen you want; glossy to dull satin.
If you are in a rush, you can do the job in five days. I generally take a week or a bit more. Each rub-out and application takes about 15 minutes. It stands up to weather very well. Just don't quit after six applications because it looks good.
