what is the most effective way of clearing the lights?
 

automotive brake cleaner melts the plastic

acetone doesn't take all the paint off

here's my experience from plastic model windows. Some times there are scratches on it and sometimes glue accidentally gets on them... so I use very fine grit sandpaper (maybe 1500 grit and wet sanding) and sand it down evenly. In your case, sand it down until u get a smooth feel. Wash the peice in soapy water. U can use turtle wax or floor polish for this step. get a cloth, and in a circular motion buff the plastic. It should get clearer and clearer... since u are polishing a lens, it might be harder cuz it's such a small peice. Don't use a dremel cuz the friction of the buffer will melt the plastic.

another option
 

find a cheap toy that's got a thick plastic bubble or buy a cheap lexan body from your LHS, take the tailights out of your car and use them as a stencil to cut the plastic bubble/lexan and use that to replace the red lenses, this way you don't ruin the lenses by accident and can go back to red if you wish.

if you wanna clear the tails on the civic the paint is on the outside of the lens at least mine was. then you just scratch the paint off gently with a razor knife or similar tool

I'm afraid I'd scratch the plastic with a razor. :o

cover up the scratches with clear nail polish

Brake fluid *might* work, but I doubt it. I know it works on spray paint.

I found the best thing for XMOD lenses. All you do is soak them and wipe, soak and wipe... This is it...goof-off

You can buy it at most hardware stores. It somes in sprays also. The one I posted is the one I used.