There are some prior threads on painting wood that might have answers in them that you'd find useful Matt. In case it's not covered in one of them, here's one of the simplest methods for painting wooden stocks.
Ppaint them a light brown, then lightly streak them with a dark colour. Don't worry about whether it ends up a bit too contrasty, the next steps will reduce this. Next do some preliminary shading with thin layers of a darker brown, paying attention to the angle the weapon will be after assembly.
Then you glaze over everything with a transparent reddish- or dark-brown colour, depending on what the woodwork is like on the weapon in question. If you have oils and acrylics available it's very easy to do the underpainting steps in acrylic, then use oils (something like Burnt Sienna or Burnt Umber) to glaze on top of it but you can do the entire thing in acrylics*.
After this you can add a bit more shading with some glazes of dark brown or black if you feel it's necessary, then use whatever you have (acrylic medium, varnish, linseed oil, Klear) to add an appropriate sheen.
This same basic approach can be used to paint belts and other leather items too, yielding effective results without too much sweat.
*Easy to mix a reddish brown, even completely from scratch if necessary, if you don't have one.
Einion