First hire a credit cleaning company. This will cost you roughly $200 USD.
I ignore my credit till I require it, then use a credit cleaner, because the entire credit report industry is pretty much a racket.
All manner of junk shows up on credit reports over the years. You can clean all this yourself + likely paying $200 will be far more profitable, than spending many hours/day for months to do this yourself.
Last time I did this my mid score was 618 + after a month of my credit cleaner's work, my mid score as 796.
You'll still require much more than a high credit score to get this type of loan + having a high credit score will ease all your steps.