Panel line help

And oh yeah... Welcome to the forum

I don't think it has as much to do with the dilution of the wash as it does the layer of Future.  The lamp black oil by itself could have dissolved a coat of enamel as well.  It could be the cure time of the future or more likely an uneven coat that is allowing the wash to penetrate the acrylic layer.

For panel lines I avoid that whole "what wash for what paint" thing by using a pastel wash.  Finley grind some chalk pastels... not oil... and mix with a some water and a drop or 2 of liquid dish soap and brush this over the panel lines.  I grind mine with a mortar& pestle but rubbing it on some fine sandpaper works well too.   Still need the gloss coat or it will satin flat paint and is a female dog to get off.  Make a small pad of paper towel, wet it, and them squeeze as much water out as you damp.  Wipe from back to front.  Since it's water this can be used over any type of clear coat.  The only thing added tot he bottom pic are some pastel airflow streaks.

 If you are going to use an oil color, you should thin your wash roughly 75%. I would say that you let it dry to long before touching up and cleanin up. I would suggest applying your wash thinned this way. Then, use a second clean brush moistened with your thinning agent to touch up and clean up the area you aplied the wash to. Be careful not to use to much thinning agent on the second brush. If you flood the area, you will remove the wash and end up with a lamp black filter on your panels. I hope this helps. Let me know how this works for you.

Thank you!

So, should I make a wash of water and soap mixed with the paint? What ratios should I use, and what should I use to clean it up with? Mineral spirits?

Thanks again.

Mineral spirit percentage of yr wash is too strong. Try some premixing to dilute it.

Usually my wash consist of black poster paste mixed with water and soap. So its totally harmless to any coat or painting and can be washed off easily if I mess it up.