Originally Posted by rhyary
So I will have to grind the paint/powdercoat so the strap itself will make conductive contact with the metal. Hmm, rust comes to mind. Also, is it importand for the strap to be short?
Yup, yup and yup. The rust issue is major from both the truck and radio viewpoints (rust some place is often why a good install goes bad). You obviously don't want to go to all this trouble to make a clean install to only have your frame and body start rusting away, so you do need to balance the technical need for a good connection against ruining your truck.
As far as removing paint, scuff it to expose some bare metal and when you clamp down the braid it will hopefully contact as much as possible. This is where I use the dielectrical grease. Another option is to paint back over the connection or glop it with silicone or wipe grease on top of it periodically. I use dielectric grease under and all over the connection and periodically clean and re-do. Anti-seize with copper is a good rust preventer and stays around better than dielectric grease. There are probably paints that conduct, but IME powdercoat is pretty lousy conductor and I've gotten a mild RF burn from a poorly ground antenna that could not couple across powdercoat.
Braid, like all grounds and powers for that matter, should be long enough to make the connection without being mechanically stressed. Longer doesn't help you at all with feedlines for power or RF. There are specific reason why you'd want specific lengths, but for anything we are talking about here you want everything just long enough.
Literally everything about a mobile radio installation is a compromise, so you work with whatcha got. IMVHO you should definitely put braid in the locations on the bumper around the antennas and maybe a couple to make sure the body of the truck connects to the frame and the one from the battery to the frame. You only expose a handful of spots to corrosion and you keep it manageable.