A detailing mate helped me tidy up the Bullbar on my old XG and said that before any polishing it needs to be acid washed..............Possibly because otherwise you're only trying to polish dirt?
We used a product that's now almost impossible to get called 'HIPO', but California Custom's 'Original Purple Metal Polish' does almost as good a job.
I had to do the Ute bars by hand but as your Van is mostly flat it shouldn't be as difficult.
The Original.
After Acid Wash
After Polish
