Clean install OS X Catalina on iMac 27" using usb flash drive

Kijana

Posts: 63   +2
Hi, am looking for a way to install macOS Catalina on a client's iMac. So far I've downloaded dmg packages for mountain lion, mojave and several catalina packages but I can't get it to work. I've used transmac and balenaEtcher to prepare my flash drives (2 thumb sticks) and am really frustrated. Any insights into where I might be getting it wrong are welcome.
I am using a pc to download the OS packages and also to prepare the flash disks.
Internet recovery keeps on timing out.
Thank you in advance.