When I was active with such things, we could not paint the coupler. The idea was that might hide defects.
The new batch or RPS Ford Pickup's hit the work bench this morning. The Santa Fe lettering came off much easier than the BN lettering.
Nice! Are they going to all be BNSF? Have any details planned for them? Here's a set I found that you might find useful. Come to think of it, I need these too. I am waiting for another product Showcase is developing, and have a few items in my mental shopping cart for my next order. No affiliation, just a satisfied customer. They have lots of other useful products and details for vehicles too. https://www.showcaseminiatures.net/n_scale/n_scale_century_foundry_accessories/45.html
Some 91% alcohol and a q-tip. You can see the one for the black BN letting in the background. Not all BNSF. I should have some decals on them and a pic tomorrow. As for details, yes, I plan to add some but haven't gotten any just yet. That Showcase Miniatures kit looks sweet as do the AllScaleMiniatures details that George is using.
If you don't have to have white lettering, you can make your own decals with your own printer using decal paper and sealing spray paint.
Here's a first look. I of each style in BNSF, ! CAT service utility truck, and one John Deere pick up that can be sales, service or delivery I guess. The BNSF decals are from Oddball decals and about 10 to 15 years or more old while the others I picked up at a train show probably 15 years ago. I see a couple that I am going to redo but at least you get the idea.