You'll need to have them sandblasted before you have them powdercoated. You'll hear some people tell you otherwise, but trust me on this.
To remove the front bumper:
You'll need an 18MM socket, a ratchet w/ a 3-4" extension and a regular screw driver.
1. Disconnect your DRLs
2. Pop the little round plugs on the plastic valence to get to the top bolts on the frame.
3. Remove the center piece on the lower part of the grill. It makes accessing things easier.
4. Remove the bolts on the bottom of the frame first, then the tops.
5. Then just pull the bumper straight forward.
The rear bumper is almost as easy.
I think the socket sizes are 15MM and 13MM. You'll also need a regular screwdriver.
1. On the corner plastic pieces you'll find little plastic buttons that need to be popped out. Use the screwdriver to pop out the little center locks slightly and then remove the button.
2. Carefully pull the center plastic piece (that has HUMMER on it) off. There are plastic clips on the back that you don't want to snap off. Just be careful & you'll be ok.
3. Remove the nuts from the support struts behind the bumper.
4. Remove the bolts that hold the D-rings.
5. Remove the smaller bolts/screws behind the D-rings
6. The bumper can now be lifted off.
While you have the D-rings off you might want to sand them and repaint them. They're notorious for rusting.
I'm really tired, so I might be forgetting something.