I'm not here to share relic techniques, but these tips may help you.
Oh no, one unexpected ding, what do I do?!
As you may know, nitrocellulose finishes are a lot thinner than polyurethane finishes. They are also a lot more fragile. That's the reason they age quite faster, and that's why we like them, right?! If not, relic wouldn't be possible.
Eventually, you will have new dings on your guitar body or neck one of these days. What should you do without spending a lot of money, and when your guitar tech or luthier skills are not that developed?
Q-tips are your friends! If you have a bit of nitro that came off and now the wood behind it is showing, don't panic. Apply some white vinegar with a Q-tip on the spot; that will give it a grey vintage look. Let it dry by itself, and if it's not dark enough, repeat the process. When dry, you can then apply a bit of neutral shoe wax, or even dark shoe wax and polish that spot by hand easily. The wax will protect the wood and the finish. If you want to color it, there are water or alcohol-based tints in the market, but go easy on it. If it's too much, the nitro can be melted slightly.
How about metal parts?
I personnally would advise you to, once or twice a year apply some WD40 or similar in your moving parts, like tuners, saddles, etc. Rust is rust, and Custom Shop or not, they may get stiff one of these days.
Cleaning.
Nothing too facy; those neutral furniture sprays from any supermarket are great for it, or (my favourite!) some drops of bee wax can restore the shine and help the wood not to dry too much.
All for now!
God bless ;)