I'm in the middle of doing the bodywork on a truck at work and thought I'd document the process of detail sanding around the various panel shapes, flanges, and stamped details. You can have the flat panels laser straight but if the other areas aren't detailed then the the bodywork still needs work.
This is the panel I'm working on. Has a raised area around the fender openings that wraps back around the sides and top, corners that have flanges that meet up almost against the raised stampings. The front bed corner wraps around and has a flat area stamped in it so I'll show how to keep the edges of the flat area crisp. It's already been metalworked, and the rough bodywork is done and has three coats of Slick Sand. Slick Sand is perfect for this since it builds thick enough that you have material to work with to get everything straight.
I started by making a sanding block that fits the shape of the panel that needs shaping. Remember that bodywork is about shaping first, not smoothing. Smoothing comes after the panel is shaped properly. This was all done with 80 grit to shape the panels flat, then I use 180 to smooth everything enough for the next step of paint prep. Using a guide coat is a must when doing this to show exactly where and how much you're sanding.
This block is just a paint paddle cut in half and glued together, then the edges were trued up and one corner was rounded to match the shape of the spot I was sanding. I wrapped it with a layer of tape for bit of padding. If you use paint paddles, make sure they are square and flat, many are bowed in the middle and aren't fit for getting your panels flat!
This is the area that was sanded with the homemade block, round on one side against the raised stamping, and squared edges on the left side against the flange.
You can see where I sanded against the flange all the way down, even in the area at the bottom where that section of the panel is flat. I'll blend the flat area into the sanded area against the flange later. This way the flat area and the sanded area against the flange are on the exact same level.
Once the area beside the flange was sanded flat, I re-guidecoated it.
Next I sanded the flat area at the bottom using a long/skinny Durablock with rounded edges. I wrapped the sandpaper around the edges and let the edge of the block define the lower edge of the raised stamping. This way the edge of the stamping has an even radius down it's length, and the edge is dead straight as well. Notice the sanding scratches are in a "X" pattern- don't sand parallel with the edge of the stamping or you'll cut a second groove on the outside of the block into the flat area!
You can see that the area I sanded first with the homemade block is still shaded with guidecoat, indicating that the flat area isn't level with the area against the flange yet. Keep sanding until you start cutting into the guidecoat to make both areas level with each other. You can also see how I used a couple layers of masking tape to protect the edge of the flange from being damaged by sanding against it.
Guidecoat against flange is starting to sand off, both area are level.
Underside of raised stamping has been cut evenly across. I like to cut into these type areas enough until you start to hit bare metal. Primer usually builds up thicker in concave areas so this way the primer isn't thick enough to crack later.
