I use polyWatch from Stark Industries, a German company or Greygate Plastic Polish to enhance clear parts.
Greygate Polish for most clear parts of Airfix and Japanese kits. While Greygate will improve Revell and Eastern European kits clear parts polyWatch polish seems to give and even clearer finish on these kits.
The canopy of the Special Hobby He 178 V-1 below was polished with polyWatch.