(the subject is so important that it needs it's own thread !!! )
If you are really advanced, you can actually start from unlocking the bootloader via SPFT (before you get to TWRP or SuperSU). Download SP-Flash-Tool-R1-HD-bootloader-unlock.zip package from : http://rootjunkysdl.com/files/?dir=B...%20HD%20Amazon . Load the scatter file, Download frp partition. Then : adb reboot bootloader ; fastboot oem unlock ; fastboot format userdata ; fastboot reboot With the unlocked bootloader, you could boot into TWRP via the fastboot command :
fastboot boot twrp.img
For the more "normal" path, copy TWRP into recovery partition, as per the instructions below :
1) copy SuperSu to /sdcard (internal storage):
2) download SP flash tools, the latest version (5.1628):
3) download the TWRP package from here (Prime BLU R1) :
http://rootjunkysdl.com/files/?dir=B...%20HD%20Amazon ( TWRP_Scatter_R1_Prime.zip )
4) install MTK preloader drivers on your PC (these have to kick in when you plug in your BLU in the off state to the USB port). Thanks to @Tzul for providing a link to the signed version of the drivers for Win 8/10 :
5) run SP flash tools, select scatter file from 3)
6) flash TWRP into recovery partition (Download option in SP Flash tools). Specifically, first select "Recovery" partition only via the checkbox (see the attached image on how SPFT will look like), push the "Download" button. Turn off your BlU R1, and then plug it into the USB port. The preloader runs as BLU is trying to boot up, and that is where SPFT will kick in.. Note that if BLU is booted up, it's way too late for SPFT to work!
7) Once SP Flash tools is done, press "Pwr" + "Vol+" on BLU R1, choose boot into recovery
8) In TWRP, first mount /system partition as read only, and back up all system partitions (optional, but highly recommended !!! )
9) Install SuperSu zip from 1), and reboot into system
10) If you care to use apps like ES File Explorer (those that are not updated yet to handle system-less root), you'll need to run these commands in adb :
adb shell su mount -o remount,rw /system mount -o remount,rw / touch /sbin/su /system/bin/su /system/xbin/su mount -o remount,ro /system mount -o remount,ro /
Note, SuperSu will go for "systemless" root, and will patch boot.img. The original boot.img will be saved as /data/stock_boot_*.img.gz It's highly recommended that you backup this boot.img elsewhere (off the device), in order to be able to restore the device and accept the OTAs.
Huge thanks to people who made this possible : @ jasonmerc, @ mrmazak, @ bullet25, @lopestom !!!!!