[flashrom] Mac Pro Mojave with AMD RX580 need to fix ROM for boot screen.

I found a link to correct the problem that many people have but no one has completed with flashrom on Mac they e 580 from Mac Pro then insert to PC to use flash program,
I would like to try to do all on MAC usin flash rom. I was able to complete install brew then flashrom but now am overwelmened by manual
here is the link with fix
https://forums.macrumors.com/threads/turn-a-new-sapphire-rx580-pulse-into-th...

I need arguments to dump rx580 ROM to file 
copy to backup
edit changes
save file
flash rx580 card

What args should I use to dump to file and then flash