I have white I believe pvc walls that are poured full of concrete. Wash was built in 05. Is it ok to use lacquer thinner to clean them? We get grease, glue etc sometimes that the bay clean acid doesn't work on.
I have the same type of walls, Royal Building system. I have has success using Stone Soap Restore. for really heavy soiled areas I use the Restore and Majic Eraser.
Be careful not to got too strong with whatever you use to clean. If you burn the finish off of the wall material with a strong acid it will make the walls more difficult to clean in the future.
I often will use methanol for things that nu wall wont take off. Its relatively inexpensive and doesnt hurt the plastics. I would be concerned about lacquer thinner melting the plastic.
Purple power, greased lightning, any degreaser with sodium hydroxide or potassium hydroxide mixed in a 5 gallon bucket with hot water at 50/50 use a brush on a pole to apply it when the wall is dry and it should come off with a garden hose rinse. Kleen Wall is an awesome product for following up. Used this method on the same type of walls after a Karcher was removed.