Agree with Spookie 3-stage Renovo is the way to go. Mine didn't look too bad but ended up needing 4 'stage one' scrubbings to shift every spot of grime. So my advice is be sparing & patient with the cleaner for multiple goings over. Also really best done in warm weather (but Not full sun) The rest is straight forward as manufacturers instructions for super results. Can't vouch for the window cleaner didn't use that.
Despite being told it couldn't be done, I also managed to iron out the wrinkled rear quarter panels. Iron set v. hot & loads of steam for heavy duty denim - its not Mohair, not a job for the faint hearted, this part was tricky & took a long time, although I did have the benefit of having removed the rear window.