clear glass ruined [ advice please ]

try  soaking  it  in  oven cleaner  overnite ( if  you  still  have  it ) then  spray  it  with  windex. wipe  it  off  and  should  be  good  to  go,,,,or  just  get  a  sheet  of  acetate  and  make  a  new  one. Only other  thing  i  can  think  of  is  get  some  ultra  fine  sanding  medium (paper or sticks )  and  sand  all  the  paint  off. all  of  these   require  you  dip  it  in  future  to restore  its  clarity  when  your  done. Good  luck :)

You could remove the clear part and fill the light cavity with Krystal Klear or white glue, it will dry transparent in about two hours. any paint work below will show right through

More than likely, you won't be able to do anything to correct the old lense.  The most common way that I know of to fix the problem is to take a piece of clear plastic that is slightly larger than the old unit, rough shape it, glue it in place and then carefully file and then sand it to shape (using progressivly finer sandpaper),  Finish it by polishing and cover w/future.The light bulb inside can be represented by drilling a small, shallow hole on one of the inside faces of the piece and then carefully adding a small drop of the proper colored pain to the hole.

I've found this method to also work very well for landing lights located in the wing leading edges. I enlarge the hole in the wing slightly and add a piece of clear plastic that is some what larger than the origional part, then go thru the file, sand & polish routine.  This gives me a clear piece with no gaps to fill and when I'm ready to paint, I simply apply a piece of tape cut to the size and shape of the clear lens and them paint.

Hope this helps a little 

 

 

Often times, a piece of clear sprue will be just about the right diameter to start with.  If not, try a crafts store like Hobby Lobby or Michael's.  They carry clear beads that when shaped properly, look great!  Good luck, and post pictures when you're done!