Having metldrpwn precompiled saves you some steps as you don't have to do the compile steps in Linux.
The quickest way I can think of is:
Reboot to Petitboot
Mount the extracted Red Ribbon from USB (with precompiled metldrpwn already included?)
Run metldrpwn and dump the eid root key to the root of the USB and then boot to GameOS.
Use C2D to create the vaild DEX bin and then flash back in GameOS.
Update to DEX FW.