Seems that many still do now know how to use the rapidfire hack. So here's how:
Step 1: Download the hack pack from Dext+ thread.
Step 2: Copy your blackshot folder from the directory you installed it in. Eg. C:\Program Files\Garena Plus\Apps\Blackshot. Paste it on your desktop.
Note: Do not copy it from C:\Program Files\Garena Plus\Apps. You need to go into the blackshot folder where you see the uninstaller. The blackshot folder you should copy is in the same folder with the uninstaller
Step 3: Rename the Blackshot folder on your desktop to "Blackshot - Copy"
Step 4: Repeat step 2.
Step 5: Copy all the edited files from Dext+ hack pack and paste it to blackshot\data\_SG\script\weapon and replace all.
Note: Do not replace the files at the wrong folder. Replace at the "Blackshot" folder at the desktop and not the "Blackshot - Copy".
Step 6: Open up the "Blackshot - Copy" folder at the desktop and you would see "launcher.exe". Run it and login and enjoy the hacks.
Tested working on (this method):
Windows 7 Professional (32 bit)
Windows 7 Home Premium (64 bit)