Thanks all for the tips and suggestions.. I finally managed to get Windows 8 installed.. And here's how I did it..
1) You absolutely have to have a Mac dvd drive / superdrive.. USB sticks did not work for me, and believe me I tried around 10 different models.. I made them all using Windows 7 USB/DVD Download tool, with my original Windows 8 Pro 64bit developer edition DVD..
2) If you removed your internal DVD drive to install a secondary HDD/SSD, you have to reconnect your old drive back, just for the install..
3) I already tried rEFIt (http://refit.sourceforge.net/) and I also tried the tip suggested here (http://www.ydramu.com/2012/09/installing-windows-8-with-bootcamp-on.html) but kept failing to get my MBP to recognize the USB drive while booting.. In ML, it recognizes the USB just fine.. But while booting, it kept coming up with the message "No bootable device -- insert boot disk and press any key".. I tried pressing buttons on my keyboard to no avail..
4) So anyhow, I plugged my old Mac internal DVD drive back, and began installing Windows 8 using BCA.. Everything was fine, when I don't know what happened, the screen turned white, and I had to restart.. After I restarted, Windows 8 installation was obviously corrupted, and I had to begin from the start again.. But guess what, now my DVD drive kept spitting the Windows 8 DVD out.. I would slot it in, and after whirring for a few seconds, it spits it out.. This spitting out of the DVD completely made my installation of Windows 8 impossible, until I resetted the SMC.. (http://support.apple.com/kb/ht3964)
5) When you're in the menu in Windows 8 installation, and it asks you if you want to reformat your HDD/SSD, please choose to reformat, as bootcamp creates a MS-FAT partition, and you want NTFS for Windows 8 to run more robustly..
6) Voila, and that's it, I now have a completely working dual-boot MBP =)