Krylon here we come!!!!! Nothing in nature has sharp "tape" edges- paint everything white (except the glass in your scope !!! LOL!!) and then stripe it with the darker paint- I would use gray not black.
At the end of the year, a bit of acetone will take it all off.....
Take the flat white and grey like Chris suggested and some of the natural brush from the area and use as a stencil, hold it a couple of inches away and shadow around it with the grey, this will make a nice looking, soft edged, effective camo job to fit your area. This is the same technique I have used on LE callouts to touch up my tac rifle (we used bow camo, it was easier to remove and dried fast but I would use the krylon for your field rifle).
Tear a piece of card and hold it against your rifle at any angle, then spray over the torn edge with your darker paint, this will give you a contoured sharp edge and a feathered blend into your lighter colour.
"I mean't to shoot the pike but the duck got in the way"
As a field expedient LE callout I have used Kling or Kerlix gauze. It is quick, easy, and light. You can put the tail of the gauze over the barrel end, then turn the wrap 90 degrees and wind it down the barrel. I keep some white duct tape in my winter callout gear to help secure it if necessary, along with over-whites, white heavy gloves, and a white face mask. But I'm usually hiding from critters that can reach back if they see me. And I don't want to paint over the camo that works for the other 8-9 months of the year.
"There is no safety for honest men except by believing all possible evil of evil men." - Edmund Burke (1729-1797)
Follow the instructions in my article on how to camoflage paint your rifle and paint the base white and then the overlay grays and khakis using the techniques in the article and you will end up with a rather nice job. Leave a bit more white than color. If needed, You can take a rag and acetone and wipe the krylon paint right back off the rifle and then paint back over it with minor effort and a bit of time.
The thread is old, but I just joined last night. I just thought I'd put my portion of my federal stimulus money in for others to put in their tool box. When I have to winter-up my rifle, it is usually enroute to a problem. So I need something quick, easy, and clean. I don't think my brothers would appreciate spray painting a rifle in the front of our rig!