The techniques the modelers in these fields use aren't the same as train modelers. For instance, the way they use the product is to touch the tip of the brush that comes with the bottle cap very lightly to molded panel lines. The product then flows into the panel line by capillary action. However, this will often result in overflow spots. The plastic modelers typically recommend cleaning these up with a cotton swab dipped in acetone or mineral spirits.
Apparently they can get away with this because their models are often bare plastic without paint. But train models are almost always painted, and unless you're both very careful and very lucky, a cotton swab dipped in solvent can remove underlying paint from the model, which is not good. The modelers I watched on YouTube recommended applying a coat of clear gloss prior to using the accent color if youi're doing this with a painted model, but this just reduces the problem.
So I decided to try the accent color on a less critical model, in this case an Athearn bluebox Maine Central boxcar. I focused on the lines around the plug door, the tack boards, and the door tracks. I started following the YouTube examples with very light touches intended to fill the lines by capillary action, but it seemed like a lot of work for not much effect. I wound up swabbing it on less delicately and cleaning things up with a piece of paper towel.
I found I definitely like what it did around the door tracks, and it also covered up uneven factory paint on the door. I did find that not only can you use a piece of paper towel to soak up excess, but you can simply smear any extra off with your finger just as easily. However, it is solvent based paint, just highly diluted, and it does dry after five minutes or so and is then hard to remove.So once I got used to the way it works with the boxcar, I decided to try it on an IC diesel. Light colored GP7s and GP9s accumulate grime between the lovers of the vents. I decided to see what I might be able to do to represent this.
What I find is that you can swab the product on the overall vents and use a small piece of paper towel to soak it up where you don't want it. I'm fairly happy with the result, but it isn't quick, and weathering a whole loco this way so far takes several hours, I'm finding.But I'll keep experimenting!