I did use AG bumper gel on the black plastics. The way I do it is apply with applicator sponge leave to soak for a while then buff and i do it every two weeks they never go gray
Now iv built up the layers.
Between aplying I just buff and it brings them
Up shiny as hell again. It's all down to
Building up layers I guess
Tried a few other products but so far this is best for me.