Hey man, good to see another Georgian on the boards! EbS are great.
As for doing the screaming as well as the singing, what you need to do is not consider screaming a completely different style of vocals, but rather just a different timbre. If you know about voiced vs voicelessness ( ie the difference between "k" and "g", "b" and "p", etc. ), what I have found is that you have to keep going, from voiceless, to voiced, to SUPER voiced, and it will cause a gravelly sound. This is what will become your screaming.