Maybe more information ? What game/playfield ? What kind of paint did you use ?

LTG : )

Could also place mylar in spots, or even install a play field protector.

Createx airbrush paint is waterbased, so protection is in order. Like Evan says partial mylar, or partial clear will protect the paint.
And after that you can wax it

You need to protect your touchup work or the ball will wear it off. Clearcoat or mylar is needed.

If you're going the clearcoat route, you need to clear the whole playfield. Spot clear will not work. It will soon lose adhesion at the edges. (Just like why body shops clear the whole hood, fender, whatever all the way to the edge of the part.)

If going the mylar route, apply a thin bit of carnuba wax to the playfield first so that the mylar can later be removed without lifting the paint.

I have done partial clear coating with varethane. Kept the games for up to 5 years and they stood up well.
I have used 2k auto clear but only on full playfields.
The varethane is not as clear as the 2pac. But is quick, easy and basically odor free. If you sell the game and the new owner freaks out about the varethane, he can remove it using xyelene without ruining the playfield.
Others mileage may vary

Varathane Poly?

https://pinside.com/pinball/forum/topic/spot-touch-up-with-clear-coat

Yes varethane poly. Water base satin or semi gloss.
I did an entire Trident playfield in varethane. Had that game for 10 years and likely played it in excess of 3000 games. It looked fabulous when I sold it. It had some dimpling but no more than my volcano that was cleared with 2pac.
For small repairs I use the brush on. For larger repairs I use the spray.
I have also used in my airbrush to seal touch ups on cabinets.

Years ago, I got a beat firepower. I did touchups with standard "deco art" brand acrylics from A.C. Moore, and then "sealed" them in with the same brand, but used a semigloss clear enamel. It made for nearly seamless touchups, and I've been cleaning and waxing over those spots for years and haven't had a problem. Seems like it could be a good option for older playfields with only small areas that need to be addressed, however.

Exactly.
Not every small touch up or every machine requires a full blown 2pac clear coat job.

If a paint is water-based does not always mean that its not durable enough. Water is only the solvent in the mix. The strength comes from the binder. There are water based epoxies that are very powerfull. That being said ,craft paints won't last very long without protection. If you dont have 2 part clear or mylar, clear fingernail polish might do in a pinch