What I did was the paint brush method. Take a two inch china bristle brush and cut off most of the bristles. Leave about an inch. Then cut out 5 or 7 notches in the bristles. I used Laural mountain forge maple and added a little nut brown to stain the stock and brown leather dye to paint the stripes.
The secret is, wood grain doesn't grow uniformly and mother nature includes what we might consider mistakes.
Don't make your stripes too uniform in width and spacing. Don't make them all perfectly parallel, in fact don't make anything "perfect" and you will get a more natural look.
That's my 2 cents, for what it's worth, that was my first attempt to paint stripes. But I like the results and will do it again.