Sometimes you will need to refurbish or restore your bumper or other chrome-plated parts, and it can be done at your own personal garage, saving you some decent cash for restoration. When you are at it, it is advisable to always start with a good core and check for fit first.
For starters, get the bumper supported on a stand and work out flaws by tapping with a hammer and dolly. Remove the dents on the bumper and then use files to refine the metal. File the common flat areas with a flat file to remove any flaws.
For those corners which are hard to reach, a bull nose file may come in handy. After that, block sand with a power sander, starting with 80 grit. For the contoured areas, make use of round PVC blocks. You can use a long power air board file for the knocking out of remaining flaws. After it is done, give the bumper a wipe down using grease remover and wax or shine.
Next, you can work on the areas which require attention such as bumper guards and their fitting. If it fits badly, you can add some wire and weld it to the inner edge. When all fits well, you can attach the bumper onto a bumper rack (if you have one) and clamp it. Cut down the copper in 180 grit, and find low spots at the same time. During plating and electric process, copper will tend to build up on the outer edges due to the amperage draws. You can take some photos to know where are the areas you want to work on first. Continue to block sand until it is quite smooth.
Next, do plating if necessary as you won't be able to apply primer using a spray gun. If there are any scratches or strikes, you will need to coat the whole bumper and block it once more. Then, for inspection, wet it down. Check for dips and other problems, and tweak them into perfection.
For copper build ups, you can use a smooth sander to knock them down nicely. It will leave you with a surface that has small curly cue on it when you are done. Put a strike on the bumper so that the smoothness can be seen and compared. Grit (320) and sand (400) the bumper and get ready for polishing. After a final wet down, the bumper should look great. Polish the copper until it has a clear and mirror-like finish. Recommended are tools like the RotoSet as well as the Roto Star from Shunner, both which may be the best tool for the job.
The smaller grooves as well as the nooks and crannys can be settled with the small RotoSet. You can use many bars of compounds. Start with rough to medium, to fine and final color from left to right. You can make use of a variety of buffs to alter the amount of space in between the threads of the buff, ranging from aggressive to refined, so you can work by trial and error to achieve the best results.
It is advisable not to use compounds of different nature on the same wheels, because once there is a certain grit coated on, it will be ingrained. You should also clean the buff in between rounds. Using a bit of 600 grit, finish off the bumper and give it a nice polish for a mirror-like finish. Apply compound now and wipe the copper down using grease remover and wax intermittently. Keep in mind that these techniques work within a professional level street rod shop so they are proven methods.
At the same time, keep your eyes open for scratches. After finishing off with the polish, grease removal as well as waxing, you are almost done, hopefully with things looking good for your car. You now have the completed section and should be ready to plate it using chrome and nickel. Following that, install it and you are done with your nice looking and sturdy bumper, which should really be worth your time and effort!