I don’t have an airbrush, but I rattle can pretty well.
As others have said, gloss coat.
If you’ve ever used Photoshop, the concept is essentially the same and you think about things in layers. However, I panel line last because some decals may cover a panel line and I soften them (or cut) to free the line.
The clear coat will serve as a buffer between types and layers of paint while also providing a smooth surface.
Gloss, is smooth while matte cures/dries/hardens with rigid crystals that deflect light. It also subsequently has a slight texture. If you ink, wash, or paint over it and then try and clean it up you will drag dissolved paint with pigment particles across a surface that will then trap that pigment. Assuming you ran in to a situation where you had a streaky mess when trying to clean the panel lines - that’s why.
Fortunately, there are a few other ways you can clean it up without having to lay yet another coat of surface (more coats can fill detail and become more difficult to work with).
If you’re using enamel, use a high polymer eraser and the enamel will peel off. Don’t wait too long or you’ll burn through the eraser, but it works in a pinch.
I sometimes use the flat edge of a hobby knife and shave off the excess. Be very careful, too shallow of an angle and you will gouge the plastic. I use this to shave a mold line on curved or complex surfaces where sanding will pose a challenge, too…so same concept. You’ll probably end up adding another topcoat anyway after decals to lock them in place (I do on waterslide since lacquer topcoats will soften decals and work air bubbles out during the degassing process.
I used the shaving method on my MG Astray last week. Since it had been almost 10 years since I really did any serious models, I did have to stumble through a process and out down some acrylic over a matte finish, completely forgetting what happens. I had metallic green dragged across a pure white piece and had to shave the topcoat off two leg vents to make them that bright white again. PITA, but kept me from having a ruined kit.