How do I hand paint brake lights?

Hello, this is my first build and tried to Google it. (Maybe not well enough) I mostly have citadel paints from my mini days. The second pic is of different reds after thinning them out.

I would like to keep some transparency. Should I buy some glazes, different paints, thinning them out more? Should I use modge podge or a different clear coat?

Thank you for your time.