I use PJ1 Special Satin Black. With black its about matching the sheen. Not too glossy, not too flat. For touch ups, spray into the cap and use a brush. It will be thin at first, so let it sit for about 10 minutes for the thinner to evaporate off.
The apron was painted with PJ1 special satin. The engine is an MTH Niagara.
https://www.amazon.com/PJ1-16-...erosol/dp/B00230I89U
Pete