This is what worked for me: used on both c1904/5 versions from scratch.

Get TowelRoot, make it rain
download SuperSu and install binaries normal way,
download init.d and busybox from Play Store and do what they are supposed to do.
Thats it, you have a fully rooted phone with init.d and busybox working on locked or unlocked bootloader. mine is locked unfortunatlly and cannot be unlocked
My Devices over the years:

Sony Xperia M - Android 4.3 Jellybean
<- Prestigio Multiphone PAP 4040 - Android 4.0.4 ICS
<- LG Optimus Me P350 - Android 2.2 Froyo
<- HTC Tytn II - Windows Mobile 6.1
<- HP 514 Voice Messenger - Windows Mobile 6
<- Sony Ericsson S500i
<- Sony Ericsson D750i
<- Nokia 6320i
<- Siemens c65
<- Siemens MT50
<- Nokia 3310