@TNump, you need a finishing spray. We used it often in the design industry to "fix" graphic design work, which, prior to digital printmaking, was a mash of paper cutouts, paint, marker, and film. We'd spray finishing spray atop it to give it a uniform, fairly abrasion-resistant (scuff, for certain) surface.
Krylon makes a version in matte, semi-gloss and gloss, as does Rustoleum.
Oh! And it can't hurt to give it a "heat glazing" prior to and after the finishing spray. Take a heat gun or hairdryer and wave over it smoothly and with even motions. Don't linger in one spot too long, but you'll be driving the moisture out of the paint and "baking" or "glazing" it. Then use the finish spray.