Step 1: Decrypt the fw you're using with PUAD or fail0verflow's tools. If using PUAD, I'd recommend selecting only dev_flash so that it'll only take a few seconds.
Step 2: Once that's complete, drop dev_flash into a folder on your desktop. Within that folder, create another folder named dev_blind.
Step 3: Without anything selected, hold down shift and right-click with your mouse. Select "Open command window here."
Step 4: Now, we'll use robocopy with this command:
Code:
robocopy [source folder] [destination folder] /Nocopy /E
P.S You may drag-and-drop the source and destination folders. By default, it'll quote the entire directory structure. If your folder location contains any folders with a space as part of its name, command prompt will assume that you're entering a command and error. It's fine if there are no spaces. However, dragging-and-dropping will prevent that mistake. Just make sure to leave a space in between the source and destination folder segments of the command line.
Step 5: With the above command, the entire folder structure of the flash will have been created, but no files were transferred. Now, drag-and-drop your modified flash files to their appropriate destinations. Once complete, enter the dev_blind directory, ctrl +A to select all folders, and create a zip file named PS3~dev_blind.zip. This will mount dev_flash as dev_blind when double-clicked within multiman. It should ask if you want to transfer all files to the locations you've specified. Select yes. Now, test if everything worked. It should unless there was a problem with one of your flash files.
Disclaimer: I am not responsible for any damage you may cause to your ps3. Just follow the instructions