A black AR-15 looks cool but it doesn't fit in well in many environments. You may wish to spray paint your AR-15 so it blends into your environment more. Cerakote is a very good way to paint a gun, but unless you have a decent spray gun your better off paying someone to do it. That is money that is probably better spent on training or upgrading your gear. Also what happens when you buy a new rail, or you want to change that flash hider? Spray painting an AR-15 yourself with a decent spray paint is a lot cheaper and is easy to paint a new rail or other part when you make changes or upgrade parts. Firearms are tools and like any tool they can get scratched with use. Done correctly a Do It Yourself paint job will hold up to a lot of use, and it can always be repainted or touched up if needed. It doesn't take a lot of talent to do a basic camo paint job.
WARNING: Painting your gun may decrease the resale value... So remember this. "Guns are for Buying. Not for Selling."
Step 1: Preparation
Remove all accessories such as optics, forward grips, flashlights, detachable backup sights ect. You should paint those items separately. You must clean your AR-15 and the accessories to be painted thoroughly before painting it. Using a degreaser on the gun to remove any oil is a good idea. Rubbing alcohol will work but isn't as good. Mask off any areas you don't want painted. Put an earplug in the muzzle device so paint doesn't get into the barrel. Close the ejection port and mask off the spring. You may wish to mask off any front sight posts, rail ID numbers, trigger, or even the serial number. If you have a collapsible stock extend the stock all the way out.
If you are painting a magazine make sure you mask off the top of the magazine where the magazine would meet the bolt carrier group. Any paint on that part of the magazine will rub off and get into the firearm.
Paint the firearm and accessories in a well ventilated area. If you do this outside do it on a day where the wind is calm. It's a good idea to do a test run on a piece of cardboard. First apply your base color. In this case I choose a sand color. Once that coat is dry you can paint an additional color in a random camo pattern by using some local foliage as a stencil. It's best to hang the rifle or accessory you are painting from something. If that isn't an option use a piece of cardboard and paint one side at a time.
Step 2: Base Coat
Apply your base coat first. Usually this will be the lightest color. Allow the paint to dry for at least an hour but preferably a day before applying any other coats of paint. Apply only a light coat of paint to the buffer tube on a collapsible stock.
Step 3: Secondary Coats
Place your stencil (I used local desert brush) against the object you are painting and paint across it.
Make sure the secondary spray paint cans are full. Once they start to get low they will not work as well. You really want to make only one pass with the secondary colors on the stencil in each area.
Allow the secondary color(s) to dry thoroughly before removing any of the masking tape.
The finished product: