Yes, correct.
You need to run d2x cios installer from that thread and install cios 249/250 and 251.
You do not need any IOS files to do that, d2x installer is all that is needed.
Then just run USB Loader GX or WiiFlow and you are set.
Instructions:
Install d2x cIOS:
11.) Launch d2x cIOS installer from the Homebrew Channel.
12.) Select cIOS : <d2x-v10-beta52-vWii> (Alternative: beta53-alt)
Select cIOS base : <56>
Select cIOS slot : <249>
13.) Press A to install and wait for installation to finish.
14.) Press A to continue.
15.) Select cIOS : <d2x-v10-beta52-vWii> (Alternative: beta53-alt)
Select cIOS base : <57>
Select cIOS slot : <250>
16.) Press A to install and wait for installation to finish.
17.) Press A to continue.
18.) Select cIOS : <d2x-v10-beta52-vWii> (Alternative: beta53-alt)
Select cIOS base : <58>
Select cIOS slot : <251>
19.) Press A to install and wait for installation to finish.
20.) Press B to Exit.
21.) Launch Wiiflow or USB Loader GX from your Homebrew Channel.
22.) Done.