Smooth-On XTC-3D™ 20 3D Print Coating, 24 oz - Brush-On Coating for 3D Printed Parts

First things first, no 3D print, especially with CF, have an "Injection molded" appearance. That being said, there are many ways to seal. A common recommendation is XTC-3D: https://www.amazon.com/Smooth-XTC-3D-Performance-Print-Coating/dp/B00PFXK4JY?th=1 The thing is, any seal is going to change the appearance. A clear seal is going to be glossy. Thicker will hide layer lines better. (as a general rule anyway)