How to: Jailbreak iOS 4 on iPhone 3GS using Pwangetool [Now Official]

iOS 4 was released yesterday and it was a big Release, Also Redsn0w 0.9.5 has already Jailbroken iPhone 3G and iPod Touch 2G, But What about iPhone 3GS users? Follow the Step by Step Guide below to Jailbreak iOS 4 final version on iPhone 3GS..
Note: This is UnOffcial Method using PwangeTool, So If you can wait a bit for Sn0wbreeze or Redsn0w then Stay away from this Method

Note: Do it on your Own Risk, we are not Responsible for Any Damage for your Device.

What you need?
iPhone 3GS running on iPhone 3.1.3 or iOS 4 GM
iTunes 9.2 From Here
iOS 4 Original Firmware From Here
Custom Pwnagetool build From Here
Update: PwangeTool 4.0 has been Released, Download From Here [Torrent] or Here [Rapidshare]
Steps:
Step 1: After Downloading iOS 4 Firmware and PwangeTool from the Links above, Open PwangeTool and Click Ok for the Copyright Window..

Step 2: Now, Choose iPhone 3GS from the next Window then Click on the blue arrow

Step 3: PwangeTool will ask you for the iOS 4 Firmware, Click on Browse and head it up to the iOS 4 you Downloaded above [iPhone2,1_4.0_8A293_Restore.ipsw]

Step 4: In the next Window, you will need to Choose some options, then Click on "Build"

Step 5: Now PwangeTool will ask you to save the Custome ipsw file, Save it to your Desktop
Step 6: You will be prompted ‘Has your iPhone 3G(S) been pwned before (does it have the pineapple logo)? If you are unsure click No.’ Then you will have your Custom ipsw

Step 7: Turnoff your iPhone device, connect it to computer via USB.
Step 8: Now hold the home button and the power button for 10 seconds and then release the power button and hold the home button for 10 seconds to enter your iPhone in DFU mode.
Step 9: PwnageTool will display a message once you successfully enter your iPhone in DFU mode. iTunes will also pop-up, Now In iTunes, hold the “Alt/Option key” and click Restore.
Step 10: Then, select the custom IPSW that was created [iPhone2,1_4.0_8A293_Custom_Restore.ipsw] and click the Open button.

Step 11: iTunes should now restore the firmware on your iPhone. This process can take around 10 minutes.
Step 12: Your iPhone 3GS will reboot automatically, Congratulations your Device is Jailbroken on iOS 4

Now you can Unlock your Device on any Baseband using Ultrasn0w.. Full Guide posted here.

This method worked for me, but if it didn't work for you (That's expected because it's not official) then wait for Sn0wbreeze V1.6 or Redsn0w 0.9.5 that will be able to Jailbreak your iPhone 3GS on iOS 4

For iPhone 3G and iPod Touch 2G owners, You can jailbreak your Device using Redsn0w 0.9.5 b5-2 [Full Guide] and Unlock using Ultrasn0w 0.93 [Full Guide] For all Basebands.

Update 1: PwangeTool 4.0 has been Released by the Dev Team, More details posted here.