By FAR the most important part is to pay a really good plater that specializes in custom car and or (preferably) motorcycle parts. Don't add any material to your parts to fix them. Let the shop do that. That is what they do. The only thing you should do is make sure your parts are as close to what you want as possible when you hand them over, and do not be shy about discussing the result you are expecting. Here is an example of what I mean. Consider a typical part like a shifter lever or kick start lever. Parts like these typically are only smoothed on the most important sides/surfaces by the factory and then plated. Often you see the coarse as-cast surface on the less important surfaces. The most bang for the buck because the labor to have parts like these polished all over is great. It will be the same for your plater (and expensive for you),as well, if you want the whole part flawless, and not even remotely stock looking if you are wanting any version of "restoration". Reproducing OEM crappy new chrome is tricky, sort of lie reproducing crappy OEM orange peel paint. Happily, if you want gorgeous flawless new chromed parts, your path is straight forward. If it is a"hard" part like the shifter mentioned, grind and polish it to be exactly like you want it to look when you get it back. (brilliantly shiny, perfect and flawlessly scratch free) Looking at your work, I am sure you can manage that (you will see why it is so expensive too, though another reason is that it is a hideously toxic process that has made it hard to do legally). That way you will know that the part will still work and be beautiful. Most parts like that can be completely perfected by removing material and without upsetting their structural requirements. If you have to add material to make it smooth enough, let them do it. Otherwise you risk contaminating your part somehow that will affect the process and have to be removed.
If it is sheet metal or anything other than a cast or forged steel part, let them do everything. I am assuming you are not plating any aluminum. I have had pretty good results following this basic concept. Even from less than high caliber platers. Good plating is a lot like painting. Shooting the paint is NOTHING, and hardly takes any time at all - like the actual plating! Getting it ready - that's the whole trick!
hope this helps
John
