I bought a bottle of Meguiar's PlastX plastic cleaner and polish yesterday. I applied it to my yucky old portlights with a microfibre rag, and rubbed it in well, on the inside and outside, then polished with a clean microfibre rag. For phase two, I reapplied it liberally to the outside again, and polished with a cotton wheel in my drill. They came out WAY better, but still could use some additional clarity. I have been thinking of removing them entirely and wetsanding them with a sequence of papers.
One au naturel
one after two phases of polish