How to: Jailbreak iOS 4 on iPhone 3GS Jailbroken 3.1.3 with Spirit [Using Spirit2Pwn]

After Sn0wbreeze V1.6.2 has been released, and it came with fixes for Youtube issues and Itunes restore errors, Still some people getting errors while Restoring! they still can't restore using custom firmwares created by PwnageTool or Sn0wbreeze. So here's a new trick or a new way to jailbreak iOS 4 on iPhone 3GS but must be Jailbroken on 3.1.3 with Spirit Using Spirit2Pwn.
Note: If you haven't jailbreak yet, then you can Jailbreak your 3.1.3 using Spirit by the guide posted here. If you are already on iOS 4 (not Jailbroken) then you can downgrade back to 3.1.3 then Jailbreak using the same guide.

Steps:
Step 1: After you got an iPhone 3GS Jailbroken on 3.1.3 with Spirit, navigate to Cydia and touch on "Manage" tab then on "Source" as in the screenshot

Step 2: Now press on "Edit" then "Add", after a window appears, Write "http://repo.woowiz.net" and press on "Add Source" as shown

Step 3: Now after adding the Source, Search for "Spirit2Pwn" and install this app.

Step 4: Your iPhone now will be ready to be Jailbroken using the custom firmwares, follow the Sn0wbreeze Guide for Windows users, and PwnageTool Guide for Mac users.

After following the guide to Jailbreak, You will be Easily able to Unlock your iPhone 3GS on any Baseband Including 05.13.04 / 05.12.01 Using Ultrasn0w 0.93, Step by Step guide posted here. [via Redmondpie]