It's covered in a film of dirt, grime or something.
Some spots were/are fine.
After using various products with a soft nylon brush for an hour, got about 3rd of it off.
Afraid to use HD stuff.
Recommendations?

thanks

Just keep doing what your doing... use nothing that has solvents in it, use only mild cleaners. Let it soak in... scrub, soak, scrub etc. Just nothing abrasive...

Good luck - Brett!

I used the POR marine clean for a lot of my cleaning chores. I was really impressed how well it cut the greasy grime. It didn't seem to damage anything I used it on.