OK, here is a step by step.
1. take the rifle apart.
2. sand down to bare metal with 220 grit sandpaper
3. after all is sanded to the metal then degrease
4. after all is degreased then you are ready to paint.
5. paint. on the stock I used the krylon fusion . I tried to primer it first and that did not work. I repeat do not primer the stock. On the bare metal I used an automotive primer and it worked great. Then after primer on the metal paint with the krylon fusion. I used olive green and khaki. after I had it all painted I stepped back a ways and used a flat black to kind of mist over the whole rifle. For the camo I just took some really old plants that had not been pulled from last year and used them for my camo pattern. I think really anything will work.
You can also follow this link and it really gives you some good ideas.
If anyone has any questions then feel free to PM and I can help you out.